diff --git a/core/src/borrow.rs b/core/src/borrow.rs
index bc026d0a44634..ccb1cc4e974d6 100644
--- a/core/src/borrow.rs
+++ b/core/src/borrow.rs
@@ -184,6 +184,7 @@ pub trait Borrow<Borrowed: ?Sized> {
 /// an underlying type by providing a mutable reference. See [`Borrow<T>`]
 /// for more information on borrowing as another type.
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_diagnostic_item = "BorrowMut"]
 pub trait BorrowMut<Borrowed: ?Sized>: Borrow<Borrowed> {
     /// Mutably borrows from an owned value.
     ///