diff -r 46f59511b7bb -r d97fdabd9e2b src/HOL/Induct/QuoDataType.thy
--- a/src/HOL/Induct/QuoDataType.thy	Fri Sep 20 19:07:10 2024 +0200
+++ b/src/HOL/Induct/QuoDataType.thy	Fri Sep 20 19:51:08 2024 +0200
@@ -30,7 +30,7 @@
 
 inductive_set
   msgrel :: "(freemsg * freemsg) set"
-  and msg_rel :: "[freemsg, freemsg] => bool"  (infixl "\<sim>" 50)
+  and msg_rel :: "[freemsg, freemsg] => bool"  (infixl \<open>\<sim>\<close> 50)
   where
     "X \<sim> Y == (X,Y) \<in> msgrel"
   | CD:    "CRYPT K (DECRYPT K X) \<sim> X"