1 files changed, 5 insertions, 0 deletions
diff --git a/src/libcore/clone.rs b/src/libcore/clone.rs
index 9a412e57294..629c197e376 100644
--- a/src/libcore/clone.rs
+++ b/src/libcore/clone.rs
@@ -227,4 +227,9 @@ mod impls {
             *self
         }
     }
+
+    // Shared references can be cloned, but mutable references *cannot*!
+    #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg(not(bootstrap))]
+    impl<T: ?Sized> !Clone for &mut T {}
 }