diff -r 46f59511b7bb -r d97fdabd9e2b src/Doc/Tutorial/Misc/fakenat.thy
--- a/src/Doc/Tutorial/Misc/fakenat.thy	Fri Sep 20 19:07:10 2024 +0200
+++ b/src/Doc/Tutorial/Misc/fakenat.thy	Fri Sep 20 19:51:08 2024 +0200
@@ -8,7 +8,7 @@
 It behaves approximately as if it were declared like this:
 \<close>
 
-datatype nat = zero ("0") | Suc nat
+datatype nat = zero (\<open>0\<close>) | Suc nat
 (*<*)
 end
 (*>*)