--- a/src/HOL/HOLCF/IOA/Storage/Action.thy	Tue Feb 13 14:24:50 2018 +0100
+++ b/src/HOL/HOLCF/IOA/Storage/Action.thy	Thu Feb 15 12:11:00 2018 +0100
@@ -10,7 +10,7 @@
 
 datatype action = New | Loc nat | Free nat
 
-lemma [cong]: "!!x. x = y ==> case_action a b c x = case_action a b c y"
+lemma [cong]: "\<And>x. x = y \<Longrightarrow> case_action a b c x = case_action a b c y"
   by simp
 
 end