diff --git a/dupe/src/__macro_refs.rs b/dupe/src/__macro_refs.rs
index 69713c3..8fe16b6 100644
--- a/dupe/src/__macro_refs.rs
+++ b/dupe/src/__macro_refs.rs
@@ -12,4 +12,4 @@
 use crate::Dupe;
 
 #[inline]
-pub const fn assert_dupe<T: Dupe + ?Sized>() {}
+pub const fn assert_dupe<T: Dupe>() {}