diff --git a/build/flags.mk b/build/flags.mk
index 1421ce6e..2562e03e 100644
--- a/build/flags.mk
+++ b/build/flags.mk
@@ -88,6 +88,7 @@ AUTO_FLAGS := \
     gen/flags/Wshadow.mk \
     gen/flags/Wsign-compare.mk \
     gen/flags/Wstrict-prototypes.mk \
+    gen/flags/Wundef-prefix.mk \
     gen/flags/bind-now.mk \
     gen/flags/deps.mk
 
diff --git a/src/bfs.h b/src/bfs.h
index 91c65408..ad6a628a 100644
--- a/src/bfs.h
+++ b/src/bfs.h
@@ -33,10 +33,15 @@
 #ifndef BFS_COMMAND
 #  define BFS_COMMAND "bfs"
 #endif
+
 #ifndef BFS_HOMEPAGE
 #  define BFS_HOMEPAGE "https://tavianator.com/projects/bfs.html"
 #endif
 
+#ifndef BFS_LINT
+#  define BFS_LINT false
+#endif
+
 // This is a symbol instead of a literal so we don't have to rebuild everything
 // when the version number changes
 extern const char bfs_version[];
diff --git a/src/fsade.c b/src/fsade.c
index 30b3018d..dfdf125c 100644
--- a/src/fsade.c
+++ b/src/fsade.c
@@ -36,6 +36,13 @@
 #  define BFS_USE_XATTR true
 #endif
 
+#ifndef BFS_USE_EXTATTR
+#  define BFS_USE_EXTATTR false
+#endif
+#ifndef BFS_USE_XATTR
+#  define BFS_USE_XATTR false
+#endif
+
 /**
  * Many of the APIs used here don't have *at() variants, but we can try to
  * emulate something similar if /proc/self/fd is available.