diff --git a/library/core/src/pin.rs b/library/core/src/pin.rs
index 9102e17d8739..ffdcd9fad49a 100644
--- a/library/core/src/pin.rs
+++ b/library/core/src/pin.rs
@@ -1829,9 +1829,10 @@ impl<Ptr, U> DispatchFromDyn<Pin<U>> for Pin<Ptr>
 ///
 /// # Safety
 ///
-/// If this type implements `Deref`, then the concrete type returned by `deref`
-/// and `deref_mut` must not change without a modification. The following
-/// operations are not considered modifications:
+/// Given a pointer of this type, the concrete type returned by its
+/// `deref` method and (if it implements `DerefMut`) its `deref_mut` method
+/// must be the same type and must not change without a modification.
+/// The following operations are not considered modifications:
 ///
 /// * Moving the pointer.
 /// * Performing unsizing coercions on the pointer.