diff -r 6b1d5b7ef45e -r 2d73c3287bd3 src/Pure/Pure.thy
--- a/src/Pure/Pure.thy	Tue Oct 15 14:55:45 2024 +0200
+++ b/src/Pure/Pure.thy	Tue Oct 15 14:57:23 2024 +0200
@@ -404,7 +404,7 @@
 
 val syntax_consts =
   Parse.and_list1
-    (Scan.optional (Scan.repeat1 Parse.name_position --| (\<^keyword>\<open>\<rightleftharpoons>\<close> || \<^keyword>\<open>==\<close>)) [] --
+    ((Scan.repeat1 Parse.name_position --| (\<^keyword>\<open>\<rightleftharpoons>\<close> || \<^keyword>\<open>==\<close>)) --
       Parse.!!! (Scan.repeat1 Parse.name_position));
 
 val _ =