diff -r 3e3e7a68cd80 -r 6ad2c917dd2e src/HOL/Library/Interval.thy
--- a/src/HOL/Library/Interval.thy	Wed Oct 09 22:01:33 2024 +0200
+++ b/src/HOL/Library/Interval.thy	Wed Oct 09 23:38:29 2024 +0200
@@ -204,7 +204,7 @@
 
 subsection \<open>Membership\<close>
 
-abbreviation (in preorder) in_interval (\<open>(_/ \<in>\<^sub>i _)\<close> [51, 51] 50)
+abbreviation (in preorder) in_interval (\<open>(\<open>notation=\<open>infix \<in>\<^sub>i\<close>\<close>_/ \<in>\<^sub>i _)\<close> [51, 51] 50)
   where "in_interval x X \<equiv> x \<in> set_of X"
 
 lemma in_interval_to_interval[intro!]: "a \<in>\<^sub>i interval_of a"