--- a/src/instance.rs	Wed Sep 03 10:08:28 2025 -0500
+++ b/src/instance.rs	Wed Sep 03 12:55:27 2025 -0500
@@ -181,7 +181,7 @@
     /// Type for a lightweight intermediate conversion that does not own the original variable.
     /// Usually this is just a reference, but may also be a lightweight structure that
     /// contains references; see the implementation for [`crate::direct_product::Pair`].
-    type Reference<'b>: Instance<X, Self>
+    type Reference<'b>: Instance<X, Self> + Copy
     where
         X: 'b;