--- a/src/HOL/Prolog/Type.thy	Fri Sep 20 19:07:10 2024 +0200
+++ b/src/HOL/Prolog/Type.thy	Fri Sep 20 19:51:08 2024 +0200
@@ -13,7 +13,7 @@
 axiomatization
   bool    :: ty and
   nat     :: ty and
-  arrow   :: "ty \<Rightarrow> ty \<Rightarrow> ty"       (infixr "->" 20) and
+  arrow   :: "ty \<Rightarrow> ty \<Rightarrow> ty"       (infixr \<open>->\<close> 20) and
   typeof  :: "[tm, ty] \<Rightarrow> bool" and
   anyterm :: tm
 where common_typeof:   "