improve comment wording

1 files changed, 2 insertions, 1 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index a47828bb63c..e36d30184c8 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -434,7 +434,8 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 found_bytes: has.bytes()
             },
         );
-        // Make sure this is non-null. (ZST references can be dereferenceable and null.)
+        // Make sure this is non-null. We checked dereferenceability above, but if `size` is zero
+        // that does not imply non-null.
         if self.ecx.scalar_may_be_null(Scalar::from_maybe_pointer(place.ptr(), self.ecx))? {
             throw_validation_failure!(self.path, NullPtr { ptr_kind })
         }