diff -r 810486f886bf -r 07a903c8cc91 src/HOL/Nominal/Examples/Class1.thy
--- a/src/HOL/Nominal/Examples/Class1.thy	Fri Nov 06 21:49:02 2015 +0100
+++ b/src/HOL/Nominal/Examples/Class1.thy	Fri Nov 06 23:31:11 2015 +0100
@@ -5189,7 +5189,7 @@
 using a2 a1
 by (induct) (auto)
 
-text {* congruence rules for \<longrightarrow>\<^sub>a* *}
+text {* congruence rules for \<open>\<longrightarrow>\<^sub>a*\<close> *}
 
 lemma ax_do_not_a_star_reduce:
   shows "Ax x a \<longrightarrow>\<^sub>a* M \<Longrightarrow> M = Ax x a"