diff -r fb9c119e5b49 -r d804e93ae9ff src/HOL/Nominal/Examples/Class1.thy
--- a/src/HOL/Nominal/Examples/Class1.thy	Sun Aug 01 23:18:13 2021 +0200
+++ b/src/HOL/Nominal/Examples/Class1.thy	Mon Aug 02 10:01:06 2021 +0000
@@ -8,6 +8,8 @@
 
 text \<open>types\<close>
 
+no_notation not  ("NOT")
+
 nominal_datatype ty =
     PR "string"
   | NOT  "ty"