diff --git a/tests/lean/mutwf1.lean b/tests/lean/mutwf1.lean
index cc140cdd6c..dc8438c331 100644
--- a/tests/lean/mutwf1.lean
+++ b/tests/lean/mutwf1.lean
@@ -10,7 +10,7 @@ mutual
     else
       n
 end
-termination_by
+termination_by'
   invImage
     (fun
      | Sum.inl ⟨n, true⟩ => (n, 2)