src/Pure/ex/Def.thy

--- a/src/Pure/ex/Def.thy	Tue Oct 17 15:51:28 2023 +0200
+++ b/src/Pure/ex/Def.thy	Tue Oct 17 18:55:29 2023 +0200
@@ -68,7 +68,7 @@
 val _ =
   (Theory.setup o Named_Target.theory_map)
     (Simplifier.define_simproc \<^binding>\<open>expand_def\<close>
-      {lhss = [Free ("x", TFree ("'a", []))], proc = K get_def});
+      {lhss = [Free ("x", TFree ("'a", []))], passive = false, proc = K get_def});
 
 
 (* Isar command *)