diff --git a/library/core/src/ops/deref.rs b/library/core/src/ops/deref.rs
index 305861ea7b69..e46204c6246a 100644
--- a/library/core/src/ops/deref.rs
+++ b/library/core/src/ops/deref.rs
@@ -293,6 +293,7 @@ fn deref_mut(&mut self) -> &mut T {
 /// unchanged.
 #[unstable(feature = "deref_pure_trait", issue = "87121")]
 #[lang = "deref_pure"]
+#[rustc_dyn_incompatible_trait]
 pub unsafe trait DerefPure: PointeeSized {}
 
 #[unstable(feature = "deref_pure_trait", issue = "87121")]