diff --git a/native_toplevel/opttopdirs.ml b/native_toplevel/opttopdirs.ml
index 67a04508bce..e8f094fa491 100644
--- a/native_toplevel/opttopdirs.ml
+++ b/native_toplevel/opttopdirs.ml
@@ -34,7 +34,7 @@ let _ = Hashtbl.add directive_table "quit" (Directive_none dir_quit)
 
 let dir_directory s =
   let d = expand_directory Config.standard_library s in
-  let dir = Load_path.Dir.create d in
+  let dir = Load_path.Dir.create ~hidden:false d in
   Load_path.append_dir dir;
   toplevel_env :=
     Stdlib.String.Set.fold
@@ -62,7 +62,7 @@ let _ =
 let _ = Hashtbl.add directive_table "show_dirs"
   (Directive_none
      (fun () ->
-        List.iter print_endline (Load_path.get_paths ())
+        List.iter print_endline (Load_path.get_path_list ())
      ))
 
 (* To change the current directory *)
diff --git a/native_toplevel/opttoploop.ml b/native_toplevel/opttoploop.ml
index 322f656bb98..f8052dbfc2d 100644
--- a/native_toplevel/opttoploop.ml
+++ b/native_toplevel/opttoploop.ml
@@ -720,17 +720,22 @@ let set_paths () =
      but keep the directories that user code linked in with ocamlmktop
      may have added to load_path. *)
   let expand = Misc.expand_directory Config.standard_library in
-  let current_load_path = Load_path.get_paths () in
-  let load_path = List.concat [
+  let Load_path.{ visible; hidden } = Load_path.get_paths () in
+  let visible = List.concat [
       [ "" ];
       List.map expand (List.rev !Compenv.first_include_dirs);
       List.map expand (List.rev !Clflags.include_dirs);
       List.map expand (List.rev !Compenv.last_include_dirs);
-      current_load_path;
+      visible;
       [expand "+camlp4"];
     ]
   in
-  Load_path.init load_path ~auto_include:Compmisc.auto_include
+  let hidden = List.concat [
+      List.map expand (List.rev !Clflags.hidden_include_dirs);
+      hidden
+    ]
+  in
+  Load_path.init ~auto_include:Compmisc.auto_include ~visible ~hidden
 
 let initialize_toplevel_env () =
   toplevel_env := Compmisc.initial_env();
diff --git a/ocaml/.depend b/ocaml/.depend
index 720edbcb329..34869cf6884 100644
--- a/ocaml/.depend
+++ b/ocaml/.depend
@@ -1280,6 +1280,7 @@ typing/persistent_env.cmi : \
     typing/subst.cmi \
     utils/misc.cmi \
     parsing/location.cmi \
+    utils/load_path.cmi \
     utils/lazy_backtrack.cmi \
     utils/import_info.cmi \
     utils/consistbl.cmi \
@@ -4543,6 +4544,7 @@ file_formats/cmt_format.cmi : \
     typing/typedtree.cmi \
     typing/shape.cmi \
     parsing/location.cmi \
+    utils/load_path.cmi \
     utils/import_info.cmi \
     typing/env.cmi \
     utils/compilation_unit.cmi \
diff --git a/ocaml/bytecomp/bytelink.ml b/ocaml/bytecomp/bytelink.ml
index 09c7a7ebe3e..4e5e0e0c948 100644
--- a/ocaml/bytecomp/bytelink.ml
+++ b/ocaml/bytecomp/bytelink.ml
@@ -376,7 +376,7 @@ let link_bytecode ?final_name tolink exec_name standalone =
        if check_dlls then begin
          (* Initialize the DLL machinery *)
          Dll.init_compile !Clflags.no_std_include;
-         Dll.add_path (Load_path.get_paths ());
+         Dll.add_path (Load_path.get_path_list ());
          try Dll.open_dlls Dll.For_checking sharedobjs
          with Failure reason -> raise(Error(Cannot_open_dll reason))
        end;
diff --git a/ocaml/debugger/command_line.ml b/ocaml/debugger/command_line.ml
index f311295bbc1..43f4a95f402 100644
--- a/ocaml/debugger/command_line.ml
+++ b/ocaml/debugger/command_line.ml
@@ -262,7 +262,8 @@ let instr_dir ppf lexbuf =
   let new_directory = argument_list_eol argument lexbuf in
     if new_directory = [] then begin
       if yes_or_no "Reinitialize directory list" then begin
-        Load_path.init ~auto_include:Compmisc.auto_include !default_load_path;
+        Load_path.init ~auto_include:Compmisc.auto_include
+          ~visible:!default_load_path ~hidden:[];
         Envaux.reset_cache ~preserve_persistent_env:false;
         Hashtbl.clear Debugger_config.load_path_for;
         flush_buffer_list ()
@@ -278,7 +279,8 @@ let instr_dir ppf lexbuf =
           List.iter (function x -> add_path (expand_path x)) new_directory'
     end;
     let print_dirs ppf l = List.iter (function x -> fprintf ppf "@ %s" x) l in
-    fprintf ppf "@[<2>Directories: %a@]@." print_dirs (Load_path.get_paths ());
+    fprintf ppf "@[<2>Directories: %a@]@." print_dirs
+      (Load_path.get_path_list ());
     Hashtbl.iter
       (fun mdl dirs ->
          fprintf ppf "@[<2>Source directories for %s: %a@]@." mdl print_dirs
diff --git a/ocaml/debugger/loadprinter.ml b/ocaml/debugger/loadprinter.ml
index 558cb2c116d..9768c0d0de3 100644
--- a/ocaml/debugger/loadprinter.ml
+++ b/ocaml/debugger/loadprinter.ml
@@ -40,8 +40,8 @@ let rec loadfiles ppf name =
     Dynlink.loadfile filename;
     let d = Filename.dirname name in
     if d <> Filename.current_dir_name then begin
-      if not (List.mem d (Load_path.get_paths ())) then
-        Load_path.add_dir d;
+      if not (List.mem d (Load_path.get_path_list ())) then
+        Load_path.add_dir ~hidden:false d;
     end;
     fprintf ppf "File %s loaded@."
       (if d <> Filename.current_dir_name then
diff --git a/ocaml/debugger/main.ml b/ocaml/debugger/main.ml
index b504ebeee61..006e8fd5bb7 100644
--- a/ocaml/debugger/main.ml
+++ b/ocaml/debugger/main.ml
@@ -224,7 +224,8 @@ let main () =
     end;
     if !Parameters.version
     then printf "\tOCaml Debugger version %s@.@." Config.version;
-    Load_path.init ~auto_include:Compmisc.auto_include !default_load_path;
+    Load_path.init ~auto_include:Compmisc.auto_include
+      ~visible:!default_load_path ~hidden:[];
     Clflags.recursive_types := true;    (* Allow recursive types. *)
     toplevel_loop ();                   (* Toplevel. *)
     kill_program ();
diff --git a/ocaml/debugger/parameters.ml b/ocaml/debugger/parameters.ml
index e7b84c8e295..42fc89cd68d 100644
--- a/ocaml/debugger/parameters.ml
+++ b/ocaml/debugger/parameters.ml
@@ -31,7 +31,7 @@ let time = ref true
 let version = ref true
 
 let add_path dir =
-  Load_path.add_dir dir;
+  Load_path.add_dir ~hidden:false dir;
   Envaux.reset_cache ~preserve_persistent_env:false
 
 let add_path_for mdl dir =
diff --git a/ocaml/debugger/program_management.ml b/ocaml/debugger/program_management.ml
index b4a2f2d1ec1..8f6d62bf8e4 100644
--- a/ocaml/debugger/program_management.ml
+++ b/ocaml/debugger/program_management.ml
@@ -128,8 +128,9 @@ let initialize_loading () =
   end;
   Symbols.clear_symbols ();
   Symbols.read_symbols Debugcom.main_frag !program_name;
-  let dirs = Load_path.get_paths () @ !Symbols.program_source_dirs in
-  Load_path.init ~auto_include:Compmisc.auto_include dirs;
+  let Load_path.{visible; hidden} = Load_path.get_paths () in
+  let visible = visible @ !Symbols.program_source_dirs in
+  Load_path.init ~auto_include:Compmisc.auto_include ~visible ~hidden;
   Envaux.reset_cache ~preserve_persistent_env:false;
   if !debug_loading then
     prerr_endline "Opening a socket...";
diff --git a/ocaml/debugger/source.ml b/ocaml/debugger/source.ml
index b1f9b2ea767..d2045cf61b6 100644
--- a/ocaml/debugger/source.ml
+++ b/ocaml/debugger/source.ml
@@ -40,7 +40,7 @@ let source_of_module pos mdle =
         else
           acc)
       Debugger_config.load_path_for
-      (Load_path.get_paths ()) in
+      (Load_path.get_path_list ()) in
   let fname = pos.Lexing.pos_fname in
   if fname = "" then
     let innermost_module =
diff --git a/ocaml/driver/compmisc.ml b/ocaml/driver/compmisc.ml
index d1af4ab0832..c0e2a0c57e3 100644
--- a/ocaml/driver/compmisc.ml
+++ b/ocaml/driver/compmisc.ml
@@ -23,28 +23,36 @@ let auto_include find_in_dir fn =
 (* Initialize the search path.
    [dir] (default: the current directory)
    is always searched first  unless -nocwd is specified,
-   then the directories specified with the -I option (in command-line order),
-   then the standard library directory (unless the -nostdlib option is given).
+   then the directories specified with the -I option (in command line order),
+   then the standard library directory (unless the -nostdlib option is given),
+   then the directories specified with the -H option (in command line order).
  *)
 
 let init_path ?(auto_include=auto_include) ?(dir="") () =
-  let dirs =
+  let visible =
     if !Clflags.use_threads then "+threads" :: !Clflags.include_dirs
     else
       !Clflags.include_dirs
   in
-  let dirs =
-    !Compenv.last_include_dirs @ dirs @ Config.flexdll_dirs @
-    !Compenv.first_include_dirs
+  let visible =
+    List.concat
+      [!Compenv.last_include_dirs;
+       visible;
+       Config.flexdll_dirs;
+       !Compenv.first_include_dirs]
   in
-  let exp_dirs =
-    List.map (Misc.expand_directory Config.standard_library) dirs
+  let visible =
+    List.map (Misc.expand_directory Config.standard_library) visible
   in
-  let dirs =
+  let visible =
     (if !Clflags.no_cwd then [] else [dir])
-    @ List.rev_append exp_dirs (Clflags.std_include_dir ())
+    @ List.rev_append visible (Clflags.std_include_dir ())
   in
-  Load_path.init ~auto_include dirs;
+  let hidden =
+    List.rev_map (Misc.expand_directory Config.standard_library)
+      !Clflags.hidden_include_dirs
+  in
+  Load_path.init ~auto_include ~visible ~hidden;
   Env.reset_cache ~preserve_persistent_env:false
 
 (* Return the initial environment in which compilation proceeds. *)
diff --git a/ocaml/driver/main_args.ml b/ocaml/driver/main_args.ml
index efbf682af6f..d545df86b83 100644
--- a/ocaml/driver/main_args.ml
+++ b/ocaml/driver/main_args.ml
@@ -153,6 +153,11 @@ let mk_i f =
 let mk_I f =
   "-I", Arg.String f, "<dir>  Add <dir> to the list of include directories"
 
+let mk_H f =
+  "-H", Arg.String f,
+  "<dir>  Add <dir> to the list of \"hidden\" include directories\n\
+ \     (Like -I, but the program can not directly reference these dependencies)"
+
 let mk_impl f =
   "-impl", Arg.String f, "<file>  Compile <file> as a .ml file"
 
@@ -849,6 +854,7 @@ module type Common_options = sig
   val _no_absname : unit -> unit
   val _alert : string -> unit
   val _I : string -> unit
+  val _H : string -> unit
   val _labels : unit -> unit
   val _alias_deps : unit -> unit
   val _no_alias_deps : unit -> unit
@@ -1136,6 +1142,7 @@ struct
     mk_stop_after ~native:false F._stop_after;
     mk_i F._i;
     mk_I F._I;
+    mk_H F._H;
     mk_impl F._impl;
     mk_intf F._intf;
     mk_intf_suffix F._intf_suffix;
@@ -1238,6 +1245,7 @@ struct
     mk_no_absname F._no_absname;
     mk_alert F._alert;
     mk_I F._I;
+    mk_H F._H;
     mk_init F._init;
     mk_labels F._labels;
     mk_alias_deps F._alias_deps;
@@ -1346,6 +1354,7 @@ struct
     mk_no_probes F._no_probes;
     mk_i F._i;
     mk_I F._I;
+    mk_H F._H;
     mk_impl F._impl;
     mk_inline F._inline;
     mk_inline_toplevel F._inline_toplevel;
@@ -1489,6 +1498,7 @@ module Make_opttop_options (F : Opttop_options) = struct
     mk_alert F._alert;
     mk_compact F._compact;
     mk_I F._I;
+    mk_H F._H;
     mk_init F._init;
     mk_inline F._inline;
     mk_inline_toplevel F._inline_toplevel;
@@ -1602,6 +1612,7 @@ struct
     mk_no_absname F._no_absname;
     mk_alert F._alert;
     mk_I F._I;
+    mk_H F._H;
     mk_impl F._impl;
     mk_intf F._intf;
     mk_intf_suffix F._intf_suffix;
@@ -1745,7 +1756,8 @@ module Default = struct
 
   module Core = struct
     include Common
-    let _I dir = include_dirs := (dir :: (!include_dirs))
+    let _I dir = include_dirs := dir :: (!include_dirs)
+    let _H dir = hidden_include_dirs := dir :: (!hidden_include_dirs)
     let _color = Misc.set_or_ignore color_reader.parse color
     let _dlambda = set dump_lambda
     let _dparsetree = set dump_parsetree
@@ -1994,6 +2006,11 @@ module Default = struct
       (* placeholder:
          Odoc_global.include_dirs := (s :: (!Odoc_global.include_dirs))
       *) ()
+    let _H(_:string) =
+      (* placeholder:
+         Odoc_global.hidden_include_dirs :=
+           (s :: (!Odoc_global.hidden_include_dirs))
+      *) ()
     let _impl (_:string) =
       (* placeholder:
          Odoc_global.files := ((!Odoc_global.files) @ [Odoc_global.Impl_file s])
diff --git a/ocaml/driver/main_args.mli b/ocaml/driver/main_args.mli
index ce43a464353..c6b66bfe9e7 100644
--- a/ocaml/driver/main_args.mli
+++ b/ocaml/driver/main_args.mli
@@ -21,6 +21,7 @@ module type Common_options = sig
   val _no_absname : unit -> unit
   val _alert : string -> unit
   val _I : string -> unit
+  val _H : string -> unit
   val _labels : unit -> unit
   val _alias_deps : unit -> unit
   val _no_alias_deps : unit -> unit
diff --git a/ocaml/driver/makedepend.ml b/ocaml/driver/makedepend.ml
index b0bc4b56205..e0076083bce 100644
--- a/ocaml/driver/makedepend.ml
+++ b/ocaml/driver/makedepend.ml
@@ -408,7 +408,8 @@ let process_file_as process_fun def source_file =
   load_path := [];
   let cwd = if !nocwd then [] else [Filename.current_dir_name] in
   List.iter add_to_load_path (
-      (!Compenv.last_include_dirs @
+      (!Clflags.hidden_include_dirs @
+       !Compenv.last_include_dirs @
        !Clflags.include_dirs @
        !Compenv.first_include_dirs @
        cwd
@@ -609,6 +610,8 @@ let run_main argv =
         " Dump the delayed dependency map for each map file";
       "-I", Arg.String (add_to_list Clflags.include_dirs),
         "<dir>  Add <dir> to the list of include directories";
+      "-H", Arg.String (add_to_list Clflags.hidden_include_dirs),
+        "<dir>  Add <dir> to the list of include directories";
       "-nocwd", Arg.Set nocwd,
         " Do not add current working directory to \
           the list of include directories";
diff --git a/ocaml/file_formats/cmt_format.ml b/ocaml/file_formats/cmt_format.ml
index 1a82c5131a6..9e8381bb395 100644
--- a/ocaml/file_formats/cmt_format.ml
+++ b/ocaml/file_formats/cmt_format.ml
@@ -54,7 +54,7 @@ type cmt_infos = {
   cmt_args : string array;
   cmt_sourcefile : string option;
   cmt_builddir : string;
-  cmt_loadpath : string list;
+  cmt_loadpath : Load_path.paths;
   cmt_source_digest : Digest.t option;
   cmt_initial_env : Env.t;
   cmt_imports : Import_info.t array;
diff --git a/ocaml/file_formats/cmt_format.mli b/ocaml/file_formats/cmt_format.mli
index e1b233fa684..a2b6fd6c464 100644
--- a/ocaml/file_formats/cmt_format.mli
+++ b/ocaml/file_formats/cmt_format.mli
@@ -57,7 +57,7 @@ type cmt_infos = {
   cmt_args : string array;
   cmt_sourcefile : string option;
   cmt_builddir : string;
-  cmt_loadpath : string list;
+  cmt_loadpath : Load_path.paths;
   cmt_source_digest : string option;
   cmt_initial_env : Env.t;
   cmt_imports : Import_info.t array;
diff --git a/ocaml/manual/src/cmds/ocamldep.etex b/ocaml/manual/src/cmds/ocamldep.etex
index 93d6741d02b..1213cb9b1b2 100644
--- a/ocaml/manual/src/cmds/ocamldep.etex
+++ b/ocaml/manual/src/cmds/ocamldep.etex
@@ -65,6 +65,12 @@ and no dependencies are generated. For programs that span multiple
 directories, it is recommended to pass "ocamldep" the same "-I" options
 that are passed to the compiler.
 
+\item["-H" \var{directory}]
+Behaves identically to "-I", except that the "-H" directories are searched
+last.  This flag is included to make it easier to invoke "ocamldep" with
+the same options as the compiler, where "-H" is used for transitive
+dependencies that the program should not directly mention.
+
 \item["-nocwd"]
 Do not add current working directory to the list of include directories.
 
diff --git a/ocaml/manual/src/cmds/ocamldoc.etex b/ocaml/manual/src/cmds/ocamldoc.etex
index e2488f6f0a3..51022fd571c 100644
--- a/ocaml/manual/src/cmds/ocamldoc.etex
+++ b/ocaml/manual/src/cmds/ocamldoc.etex
@@ -207,6 +207,10 @@ They have the same meaning as for the "ocamlc" and "ocamlopt" commands.
 Add \var{directory} to the list of directories search for compiled
 interface files (".cmi" files).
 
+\item["-H" \var{directory}]
+Like "-I", but the "-H" directories are searched last and the program may
+not directly refer to the modules added to the search path this way.
+
 \item["-nolabels"]
 Ignore non-optional labels in types.
 
diff --git a/ocaml/manual/src/cmds/unified-options.etex b/ocaml/manual/src/cmds/unified-options.etex
index b855ba4a2bf..e74f291da86 100644
--- a/ocaml/manual/src/cmds/unified-options.etex
+++ b/ocaml/manual/src/cmds/unified-options.etex
@@ -300,6 +300,16 @@ the toplevel is running with the "#directory" directive
 (section~\ref{s:toplevel-directives}).
 }%top
 
+\notop{%
+\item["-H" \var{directory}]
+Behaves identically to "-I", except that (a) programs may not directly refer to
+modules added to the search path this way, and (b) these directories are
+searched after any "-I" directories.  This makes it possible to provide the
+compiler with compiled interface and object code files for the current program's
+transitive dependencies (the dependencies of its dependencies) without allowing
+them to silently become direct dependencies.
+}%notop
+
 \top{%
 \item["-init" \var{file}]
 Load the given file instead of the default initialization file.
diff --git a/ocaml/ocamldoc/odoc_args.ml b/ocaml/ocamldoc/odoc_args.ml
index cad9ae4a13e..8d61505931d 100644
--- a/ocaml/ocamldoc/odoc_args.ml
+++ b/ocaml/ocamldoc/odoc_args.ml
@@ -187,6 +187,7 @@ let anonymous f =
 module Options = Main_args.Make_ocamldoc_options(struct
     include Main_args.Default.Odoc_args
     let _I s = Odoc_global.include_dirs := s :: !Odoc_global.include_dirs
+    let _H s = Odoc_global.hidden_include_dirs := s :: !Odoc_global.hidden_include_dirs
     let _impl s = Odoc_global.files := !Odoc_global.files @ [Odoc_global.Impl_file s]
     let _intf s = Odoc_global.files := !Odoc_global.files @ [Odoc_global.Intf_file s]
 end)
diff --git a/ocaml/ocamldoc/odoc_global.ml b/ocaml/ocamldoc/odoc_global.ml
index 3bb1a67cd4a..221745438a0 100644
--- a/ocaml/ocamldoc/odoc_global.ml
+++ b/ocaml/ocamldoc/odoc_global.ml
@@ -24,6 +24,7 @@ type source_file =
   | Text_file of string
 
 let include_dirs = Clflags.include_dirs
+let hidden_include_dirs = Clflags.hidden_include_dirs
 
 let errors = ref 0
 
diff --git a/ocaml/ocamldoc/odoc_global.mli b/ocaml/ocamldoc/odoc_global.mli
index c85b453453b..1e3df3ec2ae 100644
--- a/ocaml/ocamldoc/odoc_global.mli
+++ b/ocaml/ocamldoc/odoc_global.mli
@@ -24,6 +24,9 @@ type source_file =
 (** The include_dirs in the OCaml compiler. *)
 val include_dirs : string list ref
 
+(** The hidden_include_dirs in the OCaml compiler. *)
+val hidden_include_dirs : string list ref
+
 (** The merge options to be used. *)
 val merge_options : Odoc_types.merge_option list ref
 
diff --git a/ocaml/ocamldoc/odoc_info.ml b/ocaml/ocamldoc/odoc_info.ml
index d4a73fe1ed9..8a80224452f 100644
--- a/ocaml/ocamldoc/odoc_info.ml
+++ b/ocaml/ocamldoc/odoc_info.ml
@@ -111,6 +111,7 @@ module Module = Odoc_module
 let analyse_files
     ?(merge_options=([] : Odoc_types.merge_option list))
     ?(include_dirs=([] : string list))
+    ?(hidden_include_dirs=([] : string list))
     ?(labels=false)
     ?(sort_modules=false)
     ?(no_stop=false)
@@ -118,6 +119,7 @@ let analyse_files
     files =
   Odoc_global.merge_options := merge_options;
   Odoc_global.include_dirs := include_dirs;
+  Odoc_global.hidden_include_dirs := hidden_include_dirs;
   Odoc_global.classic := not labels;
   Odoc_global.sort_modules := sort_modules;
   Odoc_global.no_stop := no_stop;
diff --git a/ocaml/ocamldoc/odoc_info.mli b/ocaml/ocamldoc/odoc_info.mli
index da53554f892..bb4aa1d89e3 100644
--- a/ocaml/ocamldoc/odoc_info.mli
+++ b/ocaml/ocamldoc/odoc_info.mli
@@ -1082,12 +1082,13 @@ end
 val analyse_files :
     ?merge_options:Odoc_types.merge_option list ->
       ?include_dirs:string list ->
-        ?labels:bool ->
-          ?sort_modules:bool ->
-            ?no_stop:bool ->
-              ?init: Odoc_module.t_module list ->
-                Odoc_global.source_file list ->
-                  Module.t_module list
+        ?hidden_include_dirs:string list ->
+          ?labels:bool ->
+            ?sort_modules:bool ->
+              ?no_stop:bool ->
+                ?init: Odoc_module.t_module list ->
+                  Odoc_global.source_file list ->
+                    Module.t_module list
 
 (** Dump of a list of modules into a file.
    @raise Failure if an error occurs.*)
diff --git a/ocaml/parsing/ast_mapper.ml b/ocaml/parsing/ast_mapper.ml
index 2784aee0209..8a9e908da57 100644
--- a/ocaml/parsing/ast_mapper.ml
+++ b/ocaml/parsing/ast_mapper.ml
@@ -1124,11 +1124,16 @@ module PpxContext = struct
     }
 
   let make ~tool_name () =
+    let Load_path.{ visible; hidden } = Load_path.get_paths () in
     let fields =
       [
         lid "tool_name",    make_string tool_name;
-        lid "include_dirs", make_list make_string !Clflags.include_dirs;
-        lid "load_path",    make_list make_string (Load_path.get_paths ());
+        lid "include_dirs", make_list make_string (!Clflags.include_dirs);
+        lid "hidden_include_dirs",
+          make_list make_string (!Clflags.hidden_include_dirs);
+        lid "load_path",
+          make_pair (make_list make_string) (make_list make_string)
+            (visible, hidden);
         lid "open_modules", make_list make_string !Clflags.open_modules;
         lid "for_package",  make_option make_string !Clflags.for_package;
         lid "debug",        make_bool !Clflags.debug;
@@ -1197,6 +1202,8 @@ module PpxContext = struct
           tool_name_ref := get_string payload
       | "include_dirs" ->
           Clflags.include_dirs := get_list get_string payload
+      | "hidden_include_dirs" ->
+          Clflags.hidden_include_dirs := get_list get_string payload
       | "load_path" ->
           (* Duplicates Compmisc.auto_include, since we can't reference Compmisc
              from this module. *)
@@ -1207,7 +1214,10 @@ module PpxContext = struct
               let alert = Location.auto_include_alert in
               Load_path.auto_include_otherlibs alert find_in_dir fn
           in
-          Load_path.init ~auto_include (get_list get_string payload)
+          let visible, hidden =
+            get_pair (get_list get_string) (get_list get_string) payload
+          in
+          Load_path.init ~auto_include ~visible ~hidden
       | "open_modules" ->
           Clflags.open_modules := get_list get_string payload
       | "for_package" ->
diff --git a/ocaml/parsing/ast_mapper.mli b/ocaml/parsing/ast_mapper.mli
index 25965b63792..89b6b23bb17 100644
--- a/ocaml/parsing/ast_mapper.mli
+++ b/ocaml/parsing/ast_mapper.mli
@@ -148,8 +148,8 @@ val tool_name: unit -> string
     ["ocaml"], ...  Some global variables that reflect command-line
     options are automatically synchronized between the calling tool
     and the ppx preprocessor: {!Clflags.include_dirs},
-    {!Load_path}, {!Clflags.open_modules}, {!Clflags.for_package},
-    {!Clflags.debug}. *)
+    {!Clflags.hidden_include_dirs}, {!Load_path}, {!Clflags.open_modules},
+    {!Clflags.for_package}, {!Clflags.debug}. *)
 
 
 val apply: source:string -> target:string -> mapper -> unit
diff --git a/ocaml/testsuite/tests/hidden_includes/cant_reference_hidden.ocamlc.reference b/ocaml/testsuite/tests/hidden_includes/cant_reference_hidden.ocamlc.reference
new file mode 100644
index 00000000000..caae6f73442
--- /dev/null
+++ b/ocaml/testsuite/tests/hidden_includes/cant_reference_hidden.ocamlc.reference
@@ -0,0 +1,4 @@
+File "libc/c3.ml", line 1, characters 8-11:
+1 | let x = A.x + 1
+            ^^^
+Error: Unbound module "A"
diff --git a/ocaml/testsuite/tests/hidden_includes/hidden_stays_hidden.ocamlc.reference b/ocaml/testsuite/tests/hidden_includes/hidden_stays_hidden.ocamlc.reference
new file mode 100644
index 00000000000..8ba62b877af
--- /dev/null
+++ b/ocaml/testsuite/tests/hidden_includes/hidden_stays_hidden.ocamlc.reference
@@ -0,0 +1,4 @@
+File "libc/c4.ml", line 2, characters 8-11:
+2 | let y = A.x + 1
+            ^^^
+Error: Unbound module "A"
diff --git a/ocaml/testsuite/tests/hidden_includes/liba/a.ml b/ocaml/testsuite/tests/hidden_includes/liba/a.ml
new file mode 100644
index 00000000000..22b40309256
--- /dev/null
+++ b/ocaml/testsuite/tests/hidden_includes/liba/a.ml
@@ -0,0 +1,5 @@
+type t = int
+
+let x = 1
+
+type s = Baz
diff --git a/ocaml/testsuite/tests/hidden_includes/liba_alt/a.ml b/ocaml/testsuite/tests/hidden_includes/liba_alt/a.ml
new file mode 100644
index 00000000000..e907a667ba2
--- /dev/null
+++ b/ocaml/testsuite/tests/hidden_includes/liba_alt/a.ml
@@ -0,0 +1,3 @@
+type t = string
+
+let x = "hi"
diff --git a/ocaml/testsuite/tests/hidden_includes/libb/b.ml b/ocaml/testsuite/tests/hidden_includes/libb/b.ml
new file mode 100644
index 00000000000..7e41643e960
--- /dev/null
+++ b/ocaml/testsuite/tests/hidden_includes/libb/b.ml
@@ -0,0 +1,7 @@
+type t = A.t
+
+let x : A.t = A.x
+
+let f : A.t -> A.t = fun x -> x
+
+let g : A.s -> unit = fun _ -> ()
diff --git a/ocaml/testsuite/tests/hidden_includes/libc/c1.ml b/ocaml/testsuite/tests/hidden_includes/libc/c1.ml
new file mode 100644
index 00000000000..e0e5a1fd8d9
--- /dev/null
+++ b/ocaml/testsuite/tests/hidden_includes/libc/c1.ml
@@ -0,0 +1,3 @@
+let x = B.x + 1
+
+let () = Printf.printf "%d\n" x
diff --git a/ocaml/testsuite/tests/hidden_includes/libc/c2.ml b/ocaml/testsuite/tests/hidden_includes/libc/c2.ml
new file mode 100644
index 00000000000..dee5a2e74b9
--- /dev/null
+++ b/ocaml/testsuite/tests/hidden_includes/libc/c2.ml
@@ -0,0 +1 @@
+let x = B.f B.x
diff --git a/ocaml/testsuite/tests/hidden_includes/libc/c3.ml b/ocaml/testsuite/tests/hidden_includes/libc/c3.ml
new file mode 100644
index 00000000000..88c0aa8d0d6
--- /dev/null
+++ b/ocaml/testsuite/tests/hidden_includes/libc/c3.ml
@@ -0,0 +1 @@
+let x = A.x + 1
diff --git a/ocaml/testsuite/tests/hidden_includes/libc/c4.ml b/ocaml/testsuite/tests/hidden_includes/libc/c4.ml
new file mode 100644
index 00000000000..7c14a26c835
--- /dev/null
+++ b/ocaml/testsuite/tests/hidden_includes/libc/c4.ml
@@ -0,0 +1,6 @@
+let x = B.x + 1
+let y = A.x + 1
+
+(* Typing x requires loading A's cmi.  When it is made available with -H, y
+   should fail to typecheck because direct references to A are not allowed, even
+   though it has been loaded. *)
diff --git a/ocaml/testsuite/tests/hidden_includes/libc/c5.ml b/ocaml/testsuite/tests/hidden_includes/libc/c5.ml
new file mode 100644
index 00000000000..bd0715ec1e8
--- /dev/null
+++ b/ocaml/testsuite/tests/hidden_includes/libc/c5.ml
@@ -0,0 +1,7 @@
+let _ = B.g Baz
+
+(* Type-directed disambiguation: Baz is defined in A, and even when a.cmi is
+   provided with -H this still typechecks.  It's not obvious that this is
+   necessary (rejecting this program also seems fine, in that case), but this
+   test is here to record the current behavior so any change will be
+   intentional. *)
diff --git a/ocaml/testsuite/tests/hidden_includes/not_included.ocamlc.reference b/ocaml/testsuite/tests/hidden_includes/not_included.ocamlc.reference
new file mode 100644
index 00000000000..a3c0d1055eb
--- /dev/null
+++ b/ocaml/testsuite/tests/hidden_includes/not_included.ocamlc.reference
@@ -0,0 +1,7 @@
+File "libc/c1.ml", line 1, characters 8-11:
+1 | let x = B.x + 1
+            ^^^
+Error: This expression has type "A.t" but an expression was expected of type
+         "int"
+       Type "A.t" is abstract because no corresponding cmi file was found
+       in path.
diff --git a/ocaml/testsuite/tests/hidden_includes/test.ml b/ocaml/testsuite/tests/hidden_includes/test.ml
new file mode 100644
index 00000000000..4ea735dfba6
--- /dev/null
+++ b/ocaml/testsuite/tests/hidden_includes/test.ml
@@ -0,0 +1,159 @@
+(* TEST
+(* This tests the -H flag.
+
+   The basic structure is that libc depends on libb, which depends on liba.  We
+   want to test a few things:
+
+   - Compiling libc with -I liba allows the compiler to see the type definitions
+     in liba and allows c.ml to reference it directly.
+
+   - Compiling libc with -H liba allows the compiler to see the type definitions
+     in liba, but doesn't allow c.ml to reference it directly.
+
+   - If -H and -I are are passed for two different versions of liba, the -I one
+     takes priority.
+
+   - If -H is passed twice with two different versions of liba, the first takes
+     priority.
+
+   The liba_alt directory has an alternate versions of liba used for testing the
+   precedence order of the includes.
+*)
+
+subdirectories = "liba liba_alt libb libc";
+setup-ocamlc.byte-build-env;
+
+flags = "-I liba -nocwd";
+module = "liba/a.ml";
+ocamlc.byte;
+
+flags = "-I liba_alt -nocwd";
+module = "liba_alt/a.ml";
+ocamlc.byte;
+
+flags = "-I liba -I libb -nocwd";
+module = "libb/b.ml";
+ocamlc.byte;
+{
+  (* Test hiding A completely *)
+  flags = "-I libb -nocwd";
+  module = "libc/c2.ml";
+  setup-ocamlc.byte-build-env;
+  ocamlc.byte;
+}
+{
+  (* Test hiding A completely, but using it *)
+  flags = "-I libb -nocwd";
+  module = "libc/c1.ml";
+  setup-ocamlc.byte-build-env;
+  ocamlc_byte_exit_status = "2";
+  ocamlc.byte;
+  compiler_reference = "${test_source_directory}/not_included.ocamlc.reference";
+  check-ocamlc.byte-output;
+}
+{
+  (* Test transitive use of A's cmi with -I. *)
+  flags = "-I liba -I libb -nocwd";
+  module = "libc/c1.ml";
+  setup-ocamlc.byte-build-env;
+  ocamlc.byte;
+}
+{
+  (* Test transitive use of A's cmi with -H. *)
+  flags = "-H liba -I libb -nocwd";
+  module = "libc/c1.ml";
+  setup-ocamlc.byte-build-env;
+  ocamlc.byte;
+}
+{
+  (* Test direct use of A cmi with -H. *)
+  flags = "-H liba -I libb -nocwd";
+  module = "libc/c3.ml";
+  setup-ocamlc.byte-build-env;
+  ocamlc_byte_exit_status = "2";
+  ocamlc.byte;
+  compiler_reference =
+    "${test_source_directory}/cant_reference_hidden.ocamlc.reference";
+  check-ocamlc.byte-output;
+}
+
+(* The next four tests check that -I takes priority over -H regardless of the
+   order on the command line.
+*)
+{
+  flags = "-H liba_alt -I liba -I libb -nocwd";
+  module = "libc/c1.ml";
+  setup-ocamlc.byte-build-env;
+  ocamlc.byte;
+}
+{
+  flags = "-I liba -H liba_alt -I libb -nocwd";
+  module = "libc/c1.ml";
+  setup-ocamlc.byte-build-env;
+  ocamlc.byte;
+}
+{
+  not-windows;
+  flags = "-H liba -I liba_alt -I libb -nocwd";
+  module = "libc/c1.ml";
+  setup-ocamlc.byte-build-env;
+  ocamlc_byte_exit_status = "2";
+  ocamlc.byte;
+  compiler_reference =
+    "${test_source_directory}/wrong_include_order.ocamlc.reference";
+  check-ocamlc.byte-output;
+}
+{
+  not-windows;
+  flags = "-I liba_alt -H liba -I libb -nocwd";
+  module = "libc/c1.ml";
+  setup-ocamlc.byte-build-env;
+  ocamlc_byte_exit_status = "2";
+  ocamlc.byte;
+  compiler_reference =
+    "${test_source_directory}/wrong_include_order.ocamlc.reference";
+  check-ocamlc.byte-output;
+}
+
+(* The next two tests show that earlier -Hs take priority over later -Hs *)
+{
+  not-windows;
+  flags = "-H liba_alt -H liba -I libb -nocwd";
+  module = "libc/c1.ml";
+  setup-ocamlc.byte-build-env;
+  ocamlc_byte_exit_status = "2";
+  ocamlc.byte;
+  compiler_reference =
+    "${test_source_directory}/wrong_include_order.ocamlc.reference";
+  check-ocamlc.byte-output;
+}
+{
+  flags = "-H liba -H liba_alt -I libb -nocwd";
+  module = "libc/c1.ml";
+  setup-ocamlc.byte-build-env;
+  ocamlc.byte;
+}
+
+(* Test that a hidden `A` doesn't become visible as a result of the typechecker
+   using it. *)
+{
+  flags = "-H liba -I libb -nocwd";
+  module = "libc/c4.ml";
+  setup-ocamlc.byte-build-env;
+  ocamlc_byte_exit_status = "2";
+  ocamlc.byte;
+  compiler_reference =
+    "${test_source_directory}/hidden_stays_hidden.ocamlc.reference";
+  check-ocamlc.byte-output;
+}
+
+(* Test that type-directed constructor disambiguation works through -H (at
+   least, for now). *)
+{
+  flags = "-H liba -I libb -nocwd";
+  module = "libc/c5.ml";
+  setup-ocamlc.byte-build-env;
+  ocamlc.byte;
+}
+
+*)
diff --git a/ocaml/testsuite/tests/hidden_includes/wrong_include_order.ocamlc.reference b/ocaml/testsuite/tests/hidden_includes/wrong_include_order.ocamlc.reference
new file mode 100644
index 00000000000..6863dffdf5e
--- /dev/null
+++ b/ocaml/testsuite/tests/hidden_includes/wrong_include_order.ocamlc.reference
@@ -0,0 +1,3 @@
+File "libc/c1.ml", line 1:
+Error: The files "libb/b.cmi" and "liba_alt/a.cmi" make inconsistent assumptions
+       over interface "A"
diff --git a/ocaml/testsuite/tests/self-contained-toplevel/main.ml b/ocaml/testsuite/tests/self-contained-toplevel/main.ml
index c89c0485cdf..46cb4377627 100644
--- a/ocaml/testsuite/tests/self-contained-toplevel/main.ml
+++ b/ocaml/testsuite/tests/self-contained-toplevel/main.ml
@@ -23,7 +23,7 @@ let () =
   if Sys.file_exists "foo.cmi" then Sys.remove "foo.cmi";
   let module Persistent_signature = Persistent_env.Persistent_signature in
   let old_loader = !Persistent_signature.load in
-  Persistent_signature.load := (fun ~unit_name ->
+  Persistent_signature.load := (fun ~allow_hidden ~unit_name ->
     match unit_name |> Compilation_unit.Name.to_string with
     | "Foo" ->
       let {Cmi_format.cmi_name; cmi_sign; cmi_crcs; cmi_flags} =
@@ -37,10 +37,11 @@ let () =
         }
       in
       Some { Persistent_signature.
-             filename = Sys.executable_name
-           ; cmi      = cmi
+             filename   = Sys.executable_name
+           ; cmi        = cmi
+           ; visibility = Visible
            }
-    | _ -> old_loader unit_name);
+    | _ -> old_loader ~allow_hidden ~unit_name);
   Toploop.add_hook (function
       | Toploop.After_setup ->
           Toploop.toplevel_env :=
diff --git a/ocaml/tools/objinfo.ml b/ocaml/tools/objinfo.ml
index ba958bec3bf..2e20960d9a3 100644
--- a/ocaml/tools/objinfo.ml
+++ b/ocaml/tools/objinfo.ml
@@ -107,8 +107,10 @@ let print_cmt_infos cmt =
          (match cmt.cmt_sourcefile with None -> "(none)" | Some f -> f);
   printf "Compilation flags:";
   Array.iter print_spaced_string cmt.cmt_args;
-  printf "\nLoad path:";
-  List.iter print_spaced_string cmt.cmt_loadpath;
+  printf "\nLoad path:\n  Visible:";
+  List.iter print_spaced_string cmt.cmt_loadpath.visible;
+  printf "\n  Hidden:";
+  List.iter print_spaced_string cmt.cmt_loadpath.hidden;
   printf "\n";
   printf "cmt interface digest: %s\n"
     (match cmt.cmt_interface_digest with
diff --git a/ocaml/tools/ocamlcmt.ml b/ocaml/tools/ocamlcmt.ml
index 1bb39e10cc3..31169a1877d 100644
--- a/ocaml/tools/ocamlcmt.ml
+++ b/ocaml/tools/ocamlcmt.ml
@@ -69,7 +69,10 @@ let print_info cmt =
     Printf.fprintf oc "sourcefile: %s\n" name;
   end;
   Printf.fprintf oc "build directory: %s\n" cmt.cmt_builddir;
-  List.iter (Printf.fprintf oc "load path: %s\n%!") cmt.cmt_loadpath;
+  List.iter (Printf.fprintf oc "load path (visible): %s\n%!")
+    cmt.cmt_loadpath.visible;
+  List.iter (Printf.fprintf oc "load path (hidden): %s\n%!")
+    cmt.cmt_loadpath.hidden;
   begin
     match cmt.cmt_source_digest with
       None -> ()
@@ -161,7 +164,8 @@ let record_cmt_info cmt =
                                     Annot.Idef (location_file value)))
   in
   let open Cmt_format in
-  List.iter (fun dir -> record_info "include" dir) cmt.cmt_loadpath;
+  List.iter (fun dir -> record_info "include" dir) cmt.cmt_loadpath.visible;
+  List.iter (fun dir -> record_info "include" dir) cmt.cmt_loadpath.hidden;
   record_info "chdir" cmt.cmt_builddir;
   (match cmt.cmt_sourcefile with
     None -> () | Some file -> record_info "source" file)
@@ -186,7 +190,8 @@ let main () =
           | Some _ as x -> x
         in
         Envaux.reset_cache ~preserve_persistent_env:false;
-        List.iter Load_path.add_dir cmt.cmt_loadpath;
+        List.iter (Load_path.add_dir ~hidden:false) cmt.cmt_loadpath.visible;
+        List.iter (Load_path.add_dir ~hidden:true) cmt.cmt_loadpath.hidden;
         Cmt2annot.gen_annot target_filename
           ~sourcefile:cmt.cmt_sourcefile
           ~use_summaries:cmt.cmt_use_summaries
diff --git a/ocaml/toplevel/topcommon.ml b/ocaml/toplevel/topcommon.ml
index 443fcc64f77..cba2403ca53 100644
--- a/ocaml/toplevel/topcommon.ml
+++ b/ocaml/toplevel/topcommon.ml
@@ -268,18 +268,23 @@ let set_paths ?(auto_include=Compmisc.auto_include) () =
      but keep the directories that user code linked in with ocamlmktop
      may have added to load_path. *)
   let expand = Misc.expand_directory Config.standard_library in
-  let current_load_path = Load_path.get_paths () in
-  let load_path = List.concat [
+  let Load_path.{ visible; hidden } = Load_path.get_paths () in
+  let visible = List.concat [
       [ "" ];
       List.map expand (List.rev !Compenv.first_include_dirs);
       List.map expand (List.rev !Clflags.include_dirs);
       List.map expand (List.rev !Compenv.last_include_dirs);
-      current_load_path;
+      visible;
       [expand "+camlp4"];
     ]
   in
-  Load_path.init ~auto_include load_path;
-  Dll.add_path load_path
+  let hidden = List.concat [
+      List.map expand (List.rev !Clflags.hidden_include_dirs);
+      hidden
+    ]
+  in
+  Load_path.init ~auto_include ~visible ~hidden;
+  Dll.add_path (visible @ hidden)
 
 let update_search_path_from_env () =
   let extra_paths =
diff --git a/ocaml/toplevel/topdirs.ml b/ocaml/toplevel/topdirs.ml
index 3c352c0c59b..2232e4cdc3d 100644
--- a/ocaml/toplevel/topdirs.ml
+++ b/ocaml/toplevel/topdirs.ml
@@ -75,7 +75,7 @@ let _ = add_directive "quit" (Directive_none dir_quit)
 let dir_directory s =
   let d = expand_directory Config.standard_library s in
   Dll.add_path [d];
-  let dir = Load_path.Dir.create d in
+  let dir = Load_path.Dir.create ~hidden:false d in
   Load_path.prepend_dir dir;
   toplevel_env :=
     Stdlib.String.Set.fold
@@ -110,7 +110,7 @@ let _ = add_directive "remove_directory" (Directive_string dir_remove_directory)
     }
 
 let dir_show_dirs () =
-  List.iter print_endline (Load_path.get_paths ())
+  List.iter print_endline (Load_path.get_path_list ())
 
 let _ = add_directive "show_dirs" (Directive_none dir_show_dirs)
     {
diff --git a/ocaml/typing/env.ml b/ocaml/typing/env.ml
index b34cb2c1077..7849f12efc3 100644
--- a/ocaml/typing/env.ml
+++ b/ocaml/typing/env.ml
@@ -1113,7 +1113,7 @@ let find_ident_module id env =
   match find_same_module id env.modules with
   | Mod_local data -> data
   | Mod_unbound _ -> raise Not_found
-  | Mod_persistent -> find_pers_mod (id |> modname_of_ident)
+  | Mod_persistent -> find_pers_mod ~allow_hidden:true (id |> modname_of_ident)
 
 let rec find_module_components path env =
   match path with
@@ -2695,8 +2695,10 @@ let save_signature_with_transform cmi_transform ~alerts sg modname filename =
   let cmi =
     Persistent_env.make_cmi !persistent_env modname sg alerts
     |> cmi_transform in
-  Persistent_env.save_cmi !persistent_env
-    { Persistent_env.Persistent_signature.filename; cmi };
+  let pers_sig =
+    Persistent_env.Persistent_signature.{ filename; cmi; visibility = Visible }
+  in
+  Persistent_env.save_cmi !persistent_env pers_sig;
   cmi
 
 let save_signature ~alerts sg modname filename =
@@ -2935,10 +2937,10 @@ let lookup_ident_module (type a) (load : a load) ~errors ~use ~loc s env =
       let name = s |> Compilation_unit.Name.of_string in
       match load with
       | Don't_load ->
-          check_pers_mod ~loc name;
+          check_pers_mod ~allow_hidden:false ~loc name;
           path, (() : a)
       | Load -> begin
-          match find_pers_mod name with
+          match find_pers_mod ~allow_hidden:false name with
           | mda ->
               use_module ~use ~loc path mda;
               path, (mda : a)
@@ -3546,7 +3548,10 @@ let bound_module name env =
   | exception Not_found ->
       if Current_unit_name.is name then false
       else begin
-        match find_pers_mod (name |> Compilation_unit.Name.of_string) with
+        match
+          find_pers_mod ~allow_hidden:false
+            (name |> Compilation_unit.Name.of_string)
+        with
         | _ -> true
         | exception Not_found -> false
       end
diff --git a/ocaml/typing/persistent_env.ml b/ocaml/typing/persistent_env.ml
index dc7430cf983..fd32d09c6da 100644
--- a/ocaml/typing/persistent_env.ml
+++ b/ocaml/typing/persistent_env.ml
@@ -40,13 +40,18 @@ let error err = raise (Error err)
 module Persistent_signature = struct
   type t =
     { filename : string;
-      cmi : Cmi_format.cmi_infos_lazy }
-
-  let load = ref (fun ~unit_name ->
-      let unit_name = CU.Name.to_string unit_name in
-      match Load_path.find_uncap (unit_name ^ ".cmi") with
-      | filename -> Some { filename; cmi = read_cmi_lazy filename }
-      | exception Not_found -> None)
+      cmi : Cmi_format.cmi_infos_lazy;
+      visibility : Load_path.visibility }
+
+  let load = ref (fun ~allow_hidden ~unit_name ->
+    let unit_name = CU.Name.to_string unit_name in
+    match Load_path.find_uncap_with_visibility (unit_name ^ ".cmi") with
+    | filename, visibility when allow_hidden ->
+      Some { filename; cmi = read_cmi_lazy filename; visibility}
+    | filename, Visible ->
+      Some { filename; cmi = read_cmi_lazy filename; visibility = Visible}
+    | _, Hidden
+    | exception Not_found -> None)
 end
 
 type can_load_cmis =
@@ -58,6 +63,7 @@ type pers_struct = {
   ps_crcs: Import_info.t array;
   ps_filename: string;
   ps_flags: pers_flags list;
+  ps_visibility: Load_path.visibility;
 }
 
 (* If a .cmi file is missing (or invalid), we
@@ -180,7 +186,7 @@ let save_pers_struct penv crc comp_unit flags filename =
   add_import penv modname
 
 let process_pers_struct penv check modname pers_sig =
-  let { Persistent_signature.filename; cmi } = pers_sig in
+  let { Persistent_signature.filename; cmi; visibility } = pers_sig in
   let name = cmi.cmi_name in
   let crcs = cmi.cmi_crcs in
   let flags = cmi.cmi_flags in
@@ -188,6 +194,7 @@ let process_pers_struct penv check modname pers_sig =
              ps_crcs = crcs;
              ps_filename = filename;
              ps_flags = flags;
+             ps_visibility = visibility;
            } in
   let found_name = CU.name name in
   if not (CU.Name.equal modname found_name) then
@@ -225,27 +232,29 @@ let acknowledge_pers_struct penv check modname pers_sig pm =
 let read_pers_struct penv val_of_pers_sig check modname filename ~add_binding =
   add_import penv modname;
   let cmi = read_cmi_lazy filename in
-  let pers_sig = { Persistent_signature.filename; cmi } in
+  let pers_sig = { Persistent_signature.filename; cmi; visibility = Visible } in
   let pm = val_of_pers_sig pers_sig in
   let ps = process_pers_struct penv check modname pers_sig in
   if add_binding then bind_pers_struct penv modname ps pm;
   (ps, pm)
 
-let find_pers_struct penv val_of_pers_sig check name =
+let find_pers_struct ~allow_hidden penv val_of_pers_sig check name =
   let {persistent_structures; _} = penv in
   if CU.Name.equal name CU.Name.predef_exn then raise Not_found;
   match Hashtbl.find persistent_structures name with
-  | Found (ps, pm) -> (ps, pm)
+  | Found (ps, pm) when allow_hidden || ps.ps_visibility = Load_path.Visible ->
+    (ps, pm)
+  | Found _ -> raise Not_found
   | Missing -> raise Not_found
   | exception Not_found ->
     match can_load_cmis penv with
     | Cannot_load_cmis _ -> raise Not_found
     | Can_load_cmis ->
         let psig =
-          match !Persistent_signature.load ~unit_name:name with
+          match !Persistent_signature.load ~allow_hidden ~unit_name:name with
           | Some psig -> psig
           | None ->
-            Hashtbl.add persistent_structures name Missing;
+            if allow_hidden then Hashtbl.add persistent_structures name Missing;
             raise Not_found
         in
         add_import penv name;
@@ -260,10 +269,10 @@ let describe_prefix ppf prefix =
     Format.fprintf ppf "package %a" CU.Prefix.print prefix
 
 (* Emits a warning if there is no valid cmi for name *)
-let check_pers_struct penv f ~loc name =
+let check_pers_struct ~allow_hidden penv f ~loc name =
   let name_as_string = CU.Name.to_string name in
   try
-    ignore (find_pers_struct penv f false name)
+    ignore (find_pers_struct ~allow_hidden penv f false name)
   with
   | Not_found ->
       let warn = Warnings.No_cmi_file(name_as_string, None) in
@@ -300,10 +309,10 @@ let check_pers_struct penv f ~loc name =
 let read penv f modname filename ~add_binding =
   snd (read_pers_struct penv f true modname filename ~add_binding)
 
-let find penv f name =
-  snd (find_pers_struct penv f true name)
+let find ~allow_hidden penv f name =
+  snd (find_pers_struct ~allow_hidden penv f true name)
 
-let check penv f ~loc name =
+let check ~allow_hidden penv f ~loc name =
   let {persistent_structures; _} = penv in
   if not (Hashtbl.mem persistent_structures name) then begin
     (* PR#6843: record the weak dependency ([add_import]) regardless of
@@ -312,7 +321,7 @@ let check penv f ~loc name =
     add_import penv name;
     if (Warnings.is_active (Warnings.No_cmi_file("", None))) then
       !add_delayed_check_forward
-        (fun () -> check_pers_struct penv f ~loc name)
+        (fun () -> check_pers_struct ~allow_hidden penv f ~loc name)
   end
 
 (* CR mshinwell: delete this having moved to 4.14 build compilers *)
@@ -336,7 +345,7 @@ let crc_of_unit penv f name =
   match Consistbl.find penv.crc_units name with
   | Some (_, crc) -> crc
   | None ->
-    let (ps, _pm) = find_pers_struct penv f true name in
+    let (ps, _pm) = find_pers_struct ~allow_hidden:true penv f true name in
     match Array.find_opt (Import_info.has_name ~name) ps.ps_crcs with
     | None -> assert false
     | Some import_info ->
@@ -379,7 +388,7 @@ let make_cmi penv modname sign alerts =
   }
 
 let save_cmi penv psig =
-  let { Persistent_signature.filename; cmi } = psig in
+  let { Persistent_signature.filename; cmi; _ } = psig in
   Misc.try_finally (fun () ->
       let {
         cmi_name = modname;
diff --git a/ocaml/typing/persistent_env.mli b/ocaml/typing/persistent_env.mli
index bfa3f05345d..4e4e8a2cbea 100644
--- a/ocaml/typing/persistent_env.mli
+++ b/ocaml/typing/persistent_env.mli
@@ -38,12 +38,15 @@ val report_error: Format.formatter -> error -> unit
 module Persistent_signature : sig
   type t =
     { filename : string; (** Name of the file containing the signature. *)
-      cmi : Cmi_format.cmi_infos_lazy }
+      cmi : Cmi_format.cmi_infos_lazy;
+      visibility : Load_path.visibility
+    }
 
   (** Function used to load a persistent signature. The default is to look for
       the .cmi file in the load path. This function can be overridden to load
       it from memory, for instance to build a self-contained toplevel. *)
-  val load : (unit_name:Compilation_unit.Name.t -> t option) ref
+  val load :
+    (allow_hidden:bool -> unit_name:Compilation_unit.Name.t -> t option) ref
 end
 
 type can_load_cmis =
@@ -63,12 +66,12 @@ val fold : 'a t -> (Compilation_unit.Name.t -> 'a -> 'b -> 'b) -> 'b -> 'b
    bind the module name in the environment. *)
 val read : 'a t -> (Persistent_signature.t -> 'a)
   -> Compilation_unit.Name.t -> filepath -> add_binding:bool -> 'a
-val find : 'a t -> (Persistent_signature.t -> 'a)
+val find : allow_hidden:bool -> 'a t -> (Persistent_signature.t -> 'a)
   -> Compilation_unit.Name.t -> 'a
 
 val find_in_cache : 'a t -> Compilation_unit.Name.t -> 'a option
 
-val check : 'a t -> (Persistent_signature.t -> 'a)
+val check : allow_hidden:bool -> 'a t -> (Persistent_signature.t -> 'a)
   -> loc:Location.t -> Compilation_unit.Name.t -> unit
 
 (* [looked_up penv md] checks if one has already tried
diff --git a/ocaml/typing/typemod.ml b/ocaml/typing/typemod.ml
index 9a717f44e6f..b12439ed6a5 100644
--- a/ocaml/typing/typemod.ml
+++ b/ocaml/typing/typemod.ml
@@ -210,7 +210,7 @@ let initial_env ~loc ~initially_opened_module
       env
   in
   let units =
-    List.map Env.persistent_structures_of_dir (Load_path.get ())
+    List.map Env.persistent_structures_of_dir (Load_path.get_visible ())
   in
   let env, units =
     match initially_opened_module with
diff --git a/ocaml/utils/ccomp.ml b/ocaml/utils/ccomp.ml
index 41d481b2e80..a6318cf0922 100644
--- a/ocaml/utils/ccomp.ml
+++ b/ocaml/utils/ccomp.ml
@@ -115,7 +115,8 @@ let compile_file ?output ?(opt="") ?stable_name name =
          (String.concat " " (List.rev !Clflags.all_ccopts))
          (quote_prefixed ~response_files:true "-I"
             (List.map (Misc.expand_directory Config.standard_library)
-               (List.rev !Clflags.include_dirs)))
+               (List.rev (  !Clflags.hidden_include_dirs
+                          @ !Clflags.include_dirs))))
          (Clflags.std_include_flag "-I")
          (Filename.quote name)
          (* cl tediously includes the name of the C file as the first thing it
@@ -185,7 +186,7 @@ let call_linker ?(native_toplevel = false) mode output_name files extra =
           Config.native_pack_linker
           (Filename.quote output_name)
           (quote_prefixed ~response_files:true
-            l_prefix (Load_path.get_paths ()))
+            l_prefix (Load_path.get_path_list ()))
           (quote_files ~response_files:true (remove_Wl files))
           extra
       else
@@ -201,7 +202,8 @@ let call_linker ?(native_toplevel = false) mode output_name files extra =
           ""  (*(Clflags.std_include_flag "-I")*)
           (if native_toplevel then ""
            else
-             quote_prefixed ~response_files:true "-L" (Load_path.get_paths ()))
+             quote_prefixed ~response_files:true "-L"
+               (Load_path.get_path_list ()))
           (String.concat " " (List.rev !Clflags.all_ccopts))
           (quote_files ~response_files:true files)
           extra
diff --git a/ocaml/utils/clflags.ml b/ocaml/utils/clflags.ml
index adb56fdf341..e34c9fba21a 100644
--- a/ocaml/utils/clflags.ml
+++ b/ocaml/utils/clflags.ml
@@ -46,7 +46,8 @@ let cmi_file = ref None
 
 let compile_only = ref false            (* -c *)
 and output_name = ref (None : string option) (* -o *)
-and include_dirs = ref ([] : string list)(* -I *)
+and include_dirs = ref ([] : string list) (* -I *)
+and hidden_include_dirs = ref ([] : string list) (* -H *)
 and no_std_include = ref false          (* -nostdlib *)
 and no_cwd = ref false                  (* -nocwd *)
 and print_types = ref false             (* -i *)
diff --git a/ocaml/utils/clflags.mli b/ocaml/utils/clflags.mli
index 4bdae1f5dcc..c7857f53340 100644
--- a/ocaml/utils/clflags.mli
+++ b/ocaml/utils/clflags.mli
@@ -58,6 +58,7 @@ val cmi_file : string option ref
 val compile_only : bool ref
 val output_name : string option ref
 val include_dirs : string list ref
+val hidden_include_dirs : string list ref
 val no_std_include : bool ref
 val no_cwd : bool ref
 val print_types : bool ref
diff --git a/ocaml/utils/load_path.ml b/ocaml/utils/load_path.ml
index 42330d56232..d3e41aa12e3 100644
--- a/ocaml/utils/load_path.ml
+++ b/ocaml/utils/load_path.ml
@@ -19,17 +19,22 @@ module STbl = Misc.Stdlib.String.Tbl
 (* Mapping from basenames to full filenames *)
 type registry = string STbl.t
 
-let files : registry ref = s_table STbl.create 42
-let files_uncap : registry ref = s_table STbl.create 42
+let visible_files : registry ref = s_table STbl.create 42
+let visible_files_uncap : registry ref = s_table STbl.create 42
+
+let hidden_files : registry ref = s_table STbl.create 42
+let hidden_files_uncap : registry ref = s_table STbl.create 42
 
 module Dir = struct
   type t = {
     path : string;
     files : string list;
+    hidden : bool;
   }
 
   let path t = t.path
   let files t = t.files
+  let hidden t = t.hidden
 
   let find t fn =
     if List.mem fn t.files then
@@ -56,26 +61,43 @@ module Dir = struct
     with Sys_error _ ->
       [||]
 
-  let create path =
-    { path; files = Array.to_list (readdir_compat path) }
+  let create ~hidden path =
+    { path; files = Array.to_list (readdir_compat path); hidden }
 end
 
 type auto_include_callback =
   (Dir.t -> string -> string option) -> string -> string
 
-let dirs = s_ref []
+let visible_dirs = s_ref []
+let hidden_dirs = s_ref []
 let no_auto_include _ _ = raise Not_found
 let auto_include_callback = ref no_auto_include
 
 let reset () =
   assert (not Config.merlin || Local_store.is_bound ());
-  STbl.clear !files;
-  STbl.clear !files_uncap;
-  dirs := [];
+  STbl.clear !hidden_files;
+  STbl.clear !hidden_files_uncap;
+  STbl.clear !visible_files;
+  STbl.clear !visible_files_uncap;
+  hidden_dirs := [];
+  visible_dirs := [];
   auto_include_callback := no_auto_include
 
-let get () = List.rev !dirs
-let get_paths () = List.rev_map Dir.path !dirs
+let get_visible () = List.rev !visible_dirs
+
+let get_path_list () =
+  Misc.rev_map_end Dir.path !visible_dirs (List.rev_map Dir.path !hidden_dirs)
+
+type paths =
+  { visible : string list;
+    hidden : string list }
+
+let get_paths () =
+  { visible = List.rev_map Dir.path !visible_dirs;
+    hidden = List.rev_map Dir.path !hidden_dirs }
+
+let get_visible_path_list () = List.rev_map Dir.path !visible_dirs
+let get_hidden_path_list () = List.rev_map Dir.path !hidden_dirs
 
 (* Optimized version of [add] below, for use in [init] and [remove_dir]: since
    we are starting from an empty cache, we can avoid checking whether a unit
@@ -84,51 +106,72 @@ let get_paths () = List.rev_map Dir.path !dirs
 let prepend_add dir =
   List.iter (fun base ->
       let fn = Filename.concat dir.Dir.path base in
-      STbl.replace !files base fn;
-      STbl.replace !files_uncap (String.uncapitalize_ascii base) fn
+      if dir.Dir.hidden then begin
+        STbl.replace !hidden_files base fn;
+        STbl.replace !hidden_files_uncap (String.uncapitalize_ascii base) fn
+      end else begin
+        STbl.replace !visible_files base fn;
+        STbl.replace !visible_files_uncap (String.uncapitalize_ascii base) fn
+      end
     ) dir.Dir.files
 
-let init ~auto_include l =
+let init ~auto_include ~visible ~hidden =
   reset ();
-  dirs := List.rev_map Dir.create l;
-  List.iter prepend_add !dirs;
+  visible_dirs := List.rev_map (Dir.create ~hidden:false) visible;
+  hidden_dirs := List.rev_map (Dir.create ~hidden:true) hidden;
+  List.iter prepend_add !hidden_dirs;
+  List.iter prepend_add !visible_dirs;
   auto_include_callback := auto_include
 
 let remove_dir dir =
   assert (not Config.merlin || Local_store.is_bound ());
-  let new_dirs = List.filter (fun d -> Dir.path d <> dir) !dirs in
-  if List.compare_lengths new_dirs !dirs <> 0 then begin
+  let visible = List.filter (fun d -> Dir.path d <> dir) !visible_dirs in
+  let hidden = List.filter (fun d -> Dir.path d <> dir) !hidden_dirs in
+  if    List.compare_lengths visible !visible_dirs <> 0
+     || List.compare_lengths hidden !hidden_dirs <> 0 then begin
     reset ();
-    List.iter prepend_add new_dirs;
-    dirs := new_dirs
+    visible_dirs := visible;
+    hidden_dirs := hidden;
+    List.iter prepend_add hidden;
+    List.iter prepend_add visible
   end
 
 (* General purpose version of function to add a new entry to load path: We only
-   add a basename to the cache if it is not already present in the cache, in
-   order to enforce left-to-right precedence. *)
-let add dir =
+   add a basename to the cache if it is not already present, in order to enforce
+   left-to-right precedence. *)
+let add (dir : Dir.t) =
   assert (not Config.merlin || Local_store.is_bound ());
+  let update base fn visible_files hidden_files =
+    if dir.hidden && not (STbl.mem !hidden_files base) then
+      STbl.replace !hidden_files base fn
+    else if not (STbl.mem !visible_files base) then
+      STbl.replace !visible_files base fn
+  in
   List.iter
     (fun base ->
        let fn = Filename.concat dir.Dir.path base in
-       if not (STbl.mem !files base) then
-         STbl.replace !files base fn;
+       update base fn visible_files hidden_files;
        let ubase = String.uncapitalize_ascii base in
-       if not (STbl.mem !files_uncap ubase) then
-         STbl.replace !files_uncap ubase fn)
-    dir.Dir.files;
-  dirs := dir :: !dirs
+       update ubase fn visible_files_uncap hidden_files_uncap)
+    dir.files;
+  if dir.hidden then
+    hidden_dirs := dir :: !hidden_dirs
+  else
+    visible_dirs := dir :: !visible_dirs
 
 let append_dir = add
 
-let add_dir dir = add (Dir.create dir)
+let add_dir ~hidden dir = add (Dir.create ~hidden dir)
 
 (* Add the directory at the start of load path - so basenames are
    unconditionally added. *)
-let prepend_dir dir =
+let prepend_dir (dir : Dir.t) =
   assert (not Config.merlin || Local_store.is_bound ());
   prepend_add dir;
-  dirs := !dirs @ [dir]
+  if dir.hidden then
+    hidden_dirs := !hidden_dirs @ [dir]
+  else
+    visible_dirs := !visible_dirs @ [dir]
 
 let is_basename fn = Filename.basename fn = fn
 
@@ -150,27 +193,40 @@ let auto_include_otherlibs =
   (* Ensure directories are only ever scanned once *)
   let expand = Misc.expand_directory Config.standard_library in
   let otherlibs =
-    let read_lib lib = lazy (Dir.create (expand ("+" ^ lib))) in
+    let read_lib lib = lazy (Dir.create ~hidden:false (expand ("+" ^ lib))) in
     List.map (fun lib -> (lib, read_lib lib)) ["dynlink"; "str"; "unix"] in
   auto_include_libs otherlibs
 
+type visibility = Visible | Hidden
+
+let find_file_in_cache fn visible_files hidden_files =
+  try (STbl.find !visible_files fn, Visible) with
+  | Not_found -> (STbl.find !hidden_files fn, Hidden)
+
 let find fn =
   assert (not Config.merlin || Local_store.is_bound ());
   try
     if is_basename fn && not !Sys.interactive then
-      STbl.find !files fn
+      fst (find_file_in_cache fn visible_files hidden_files)
     else
-      Misc.find_in_path (get_paths ()) fn
+      Misc.find_in_path (get_path_list ()) fn
   with Not_found ->
     !auto_include_callback Dir.find fn
 
-let find_uncap fn =
+let find_uncap_with_visibility fn =
   assert (not Config.merlin || Local_store.is_bound ());
   try
     if is_basename fn && not !Sys.interactive then
-      STbl.find !files_uncap (String.uncapitalize_ascii fn)
+      find_file_in_cache (String.uncapitalize_ascii fn)
+        visible_files_uncap hidden_files_uncap
     else
-      Misc.find_in_path_uncap (get_paths ()) fn
+      try
+        (Misc.find_in_path_uncap (get_visible_path_list ()) fn, Visible)
+      with
+      | Not_found ->
+        (Misc.find_in_path_uncap (get_hidden_path_list ()) fn, Hidden)
   with Not_found ->
     let fn_uncap = String.uncapitalize_ascii fn in
-    !auto_include_callback Dir.find_uncap fn_uncap
+    (!auto_include_callback Dir.find_uncap fn_uncap, Visible)
+
+let find_uncap fn = fst (find_uncap_with_visibility fn)
diff --git a/ocaml/utils/load_path.mli b/ocaml/utils/load_path.mli
index fe3abaf95de..757324f148c 100644
--- a/ocaml/utils/load_path.mli
+++ b/ocaml/utils/load_path.mli
@@ -14,15 +14,15 @@
 
 (** Management of include directories.
 
-    This module offers a high level interface to locating files in the
-    load path, which is constructed from [-I] command line flags and a few
+    This module offers a high level interface to locating files in the load
+    path, which is constructed from [-I] and [-H] command line flags and a few
     other parameters.
 
     It makes the assumption that the contents of include directories
     doesn't change during the execution of the compiler.
 *)
 
-val add_dir : string -> unit
+val add_dir : hidden:bool -> string -> unit
 (** Add a directory to the end of the load path (i.e. at lowest priority.) *)
 
 val remove_dir : string -> unit
@@ -35,7 +35,7 @@ module Dir : sig
   type t
   (** Represent one directory in the load path. *)
 
-  val create : string -> t
+  val create : hidden:bool -> string -> t
 
   val path : t -> string
 
@@ -43,6 +43,10 @@ module Dir : sig
   (** All the files in that directory. This doesn't include files in
       sub-directories of this directory. *)
 
+  val hidden : t -> bool
+  (** If the modules in this directory should not be bound in the initial
+      scope *)
+
   val find : t -> string -> string option
   (** [find dir fn] returns the full path to [fn] in [dir]. *)
 
@@ -59,8 +63,13 @@ val no_auto_include : auto_include_callback
 (** No automatic directory inclusion: misses in the load path raise [Not_found]
     as normal. *)
 
-val init : auto_include:auto_include_callback -> string list -> unit
-(** [init l] is the same as [reset (); List.iter add_dir (List.rev l)] *)
+val init :
+  auto_include:auto_include_callback -> visible:string list ->
+  hidden:string list -> unit
+(** [init ~visible ~hidden] is the same as
+    [reset ();
+     List.iter add_dir (List.rev hidden);
+     List.iter add_dir (List.rev visible)] *)
 
 val auto_include_otherlibs :
   (string -> unit) -> auto_include_callback
@@ -68,9 +77,16 @@ val auto_include_otherlibs :
     {!Load_path.init} and automatically adds [-I +lib] to the load path after
     calling [alert lib]. *)
 
-val get_paths : unit -> string list
+val get_path_list : unit -> string list
 (** Return the list of directories passed to [add_dir] so far. *)
 
+type paths =
+  { visible : string list;
+    hidden : string list }
+
+val get_paths : unit -> paths
+(** Return the directories passed to [add_dir] so far. *)
+
 val find : string -> string
 (** Locate a file in the load path. Raise [Not_found] if the file
     cannot be found. This function is optimized for the case where the
@@ -81,6 +97,12 @@ val find_uncap : string -> string
 (** Same as [find], but search also for uncapitalized name, i.e.  if
     name is Foo.ml, allow /path/Foo.ml and /path/foo.ml to match. *)
 
+type visibility = Visible | Hidden
+
+val find_uncap_with_visibility : string -> string * visibility
+(** Same as [find_uncap], but also reports whether the cmi was found in a -I
+    directory (Visible) or a -H directory (Hidden) *)
+
 val[@deprecated] add : Dir.t -> unit
 (** Old name for {!append_dir} *)
 
@@ -92,5 +114,6 @@ val prepend_dir : Dir.t -> unit
 (** [prepend_dir d] adds [d] to the start of the load path (i.e. at highest
     priority. *)
 
-val get : unit -> Dir.t list
-(** Same as [get_paths ()], except that it returns a [Dir.t list]. *)
+val get_visible : unit -> Dir.t list
+(** Same as [get_paths ()], except that it returns a [Dir.t list], and doesn't
+    include the -H paths. *)
diff --git a/ocaml/utils/misc.ml b/ocaml/utils/misc.ml
index 68fd23bd1a1..674b9ebd45e 100644
--- a/ocaml/utils/misc.ml
+++ b/ocaml/utils/misc.ml
@@ -70,6 +70,13 @@ let rec map_end f l1 l2 =
     [] -> l2
   | hd::tl -> f hd :: map_end f tl l2
 
+let rev_map_end f l1 l2 =
+  let rec rmap_f accu = function
+    | [] -> accu
+    | hd::tl -> rmap_f (f hd :: accu) tl
+  in
+  rmap_f l2 l1
+
 let rec map_left_right f = function
     [] -> []
   | hd::tl -> let res = f hd in res :: map_left_right f tl
diff --git a/ocaml/utils/misc.mli b/ocaml/utils/misc.mli
index 263749f7374..170c080c588 100644
--- a/ocaml/utils/misc.mli
+++ b/ocaml/utils/misc.mli
@@ -77,6 +77,9 @@ val reraise_preserving_backtrace : exn -> (unit -> unit) -> 'a
 val map_end: ('a -> 'b) -> 'a list -> 'b list -> 'b list
        (** [map_end f l t] is [map f l @ t], just more efficient. *)
 
+val rev_map_end: ('a -> 'b) -> 'a list -> 'b list -> 'b list
+       (** [rev_map_end f l t] is [map f (rev l) @ t], just more efficient. *)
+
 val map_left_right: ('a -> 'b) -> 'a list -> 'b list
        (** Like [List.map], with guaranteed left-to-right evaluation order *)
 
diff --git a/tools/flambda_backend_objinfo.ml b/tools/flambda_backend_objinfo.ml
index e9889d8ae5d..730b24640a2 100644
--- a/tools/flambda_backend_objinfo.ml
+++ b/tools/flambda_backend_objinfo.ml
@@ -113,8 +113,10 @@ let print_cmt_infos cmt =
     (match cmt.cmt_sourcefile with None -> "(none)" | Some f -> f);
   printf "Compilation flags:";
   Array.iter print_spaced_string cmt.cmt_args;
-  printf "\nLoad path:";
-  List.iter print_spaced_string cmt.cmt_loadpath;
+  printf "\nLoad path:\n  Visible:";
+  List.iter print_spaced_string cmt.cmt_loadpath.visible;
+  printf "\n  Hidden:";
+  List.iter print_spaced_string cmt.cmt_loadpath.hidden;
   printf "\n";
   printf "cmt interface digest: %s\n"
     (match cmt.cmt_interface_digest with
diff --git a/tools/merge_archives.ml b/tools/merge_archives.ml
index 2863e6da8ec..fb3aa897206 100644
--- a/tools/merge_archives.ml
+++ b/tools/merge_archives.ml
@@ -23,7 +23,7 @@ let merge_cma ~target ~archives =
   Clflags.all_ccopts := [];
   Clflags.dllibs := [];
   List.iter
-    (fun archive -> Load_path.add_dir (Filename.dirname archive))
+    (fun archive -> Load_path.add_dir ~hidden:false (Filename.dirname archive))
     archives;
   let error reporter err =
     Format.eprintf "Error whilst merging .cma files:@ %a\n%!" reporter err;