diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 275888b0ce247..bc84eccfcf56c 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -2436,8 +2436,10 @@ impl<'tcx> AdtDef {
         self.variants.iter().flat_map(|v| v.fields.iter())
     }
 
+    /// Whether the ADT lacks fields. Note that this includes uninhabited enums,
+    /// e.g., `enum Void {}` is considered payload free as well.
     pub fn is_payloadfree(&self) -> bool {
-        !self.variants.is_empty() && self.variants.iter().all(|v| v.fields.is_empty())
+        self.variants.iter().all(|v| v.fields.is_empty())
     }
 
     /// Return a `VariantDef` given a variant id.
diff --git a/compiler/rustc_mir/src/interpret/cast.rs b/compiler/rustc_mir/src/interpret/cast.rs
index 0e16b0caefafa..affeae546b2aa 100644
--- a/compiler/rustc_mir/src/interpret/cast.rs
+++ b/compiler/rustc_mir/src/interpret/cast.rs
@@ -139,9 +139,14 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
         // # First handle non-scalar source values.
 
-        // Handle cast from a univariant (ZST) enum.
+        // Handle cast from a ZST enum (0 or 1 variants).
         match src.layout.variants {
             Variants::Single { index } => {
+                if src.layout.abi.is_uninhabited() {
+                    // This is dead code, because an uninhabited enum is UB to
+                    // instantiate.
+                    throw_ub!(Unreachable);
+                }
                 if let Some(discr) = src.layout.ty.discriminant_for_variant(*self.tcx, index) {
                     assert!(src.layout.is_zst());
                     let discr_layout = self.layout_of(discr.ty)?;
diff --git a/src/test/ui/uninhabited/uninhabited-enum-cast.rs b/src/test/ui/uninhabited/uninhabited-enum-cast.rs
index 7e178e054cc4e..5a75c94c42f0b 100644
--- a/src/test/ui/uninhabited/uninhabited-enum-cast.rs
+++ b/src/test/ui/uninhabited/uninhabited-enum-cast.rs
@@ -1,7 +1,9 @@
+// check-pass
+
 enum E {}
 
 fn f(e: E) {
-    println!("{}", (e as isize).to_string());   //~ ERROR non-primitive cast
+    println!("{}", (e as isize).to_string());
 }
 
 fn main() {}
diff --git a/src/test/ui/uninhabited/uninhabited-enum-cast.stderr b/src/test/ui/uninhabited/uninhabited-enum-cast.stderr
deleted file mode 100644
index a9f10dfec994a..0000000000000
--- a/src/test/ui/uninhabited/uninhabited-enum-cast.stderr
+++ /dev/null
@@ -1,9 +0,0 @@
-error[E0605]: non-primitive cast: `E` as `isize`
-  --> $DIR/uninhabited-enum-cast.rs:4:20
-   |
-LL |     println!("{}", (e as isize).to_string());
-   |                    ^^^^^^^^^^^^ an `as` expression can only be used to convert between primitive types or to coerce to a specific trait object
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0605`.