diff --git a/src/undo_log.rs b/src/undo_log.rs
index c18a6b1..0d6d2f6 100644
--- a/src/undo_log.rs
+++ b/src/undo_log.rs
@@ -58,7 +58,6 @@ where
     }
     fn extend<I>(&mut self, undos: I)
     where
-        Self: Sized,
         I: IntoIterator<Item = T>,
     {
         U::extend(self, undos)