diff --git a/core/src/marker.rs b/core/src/marker.rs
index 62f35c1bfa2a6..a13cef26dee07 100644
--- a/core/src/marker.rs
+++ b/core/src/marker.rs
@@ -293,7 +293,7 @@ marker_impls! {
 ///
 /// ```
 /// #[derive(Clone)]
-/// struct MyStruct<T>;
+/// struct MyStruct<T>(T);
 ///
 /// impl<T: Copy> Copy for MyStruct<T> { } 
 /// ```