diff -r b23367be6051 -r 1f5428d66591 src/HOL/Map.thy
--- a/src/HOL/Map.thy	Thu Feb 23 15:37:17 2023 +0100
+++ b/src/HOL/Map.thy	Thu Feb 23 22:04:32 2023 +0100
@@ -14,7 +14,7 @@
 
 type_synonym ('a, 'b) "map" = "'a \<Rightarrow> 'b option" (infixr "\<rightharpoonup>" 0)
 
-abbreviation
+abbreviation (input)
   empty :: "'a \<rightharpoonup> 'b" where
   "empty \<equiv> \<lambda>x. None"