diff --git a/library/core/src/cmp.rs b/library/core/src/cmp.rs
index 4a15b185a83..5bab1fb93db 100644
--- a/library/core/src/cmp.rs
+++ b/library/core/src/cmp.rs
@@ -579,6 +579,7 @@ pub fn then_with<F: FnOnce() -> Ordering>(self, f: F) -> Ordering {
 /// ```
 #[derive(PartialEq, Eq, Debug, Copy, Clone, Default, Hash)]
 #[stable(feature = "reverse_cmp_key", since = "1.19.0")]
+#[repr(transparent)]
 pub struct Reverse<T>(#[stable(feature = "reverse_cmp_key", since = "1.19.0")] pub T);
 
 #[stable(feature = "reverse_cmp_key", since = "1.19.0")]