--- a/src/HOL/Library/Multiset.thy Mon Mar 22 00:07:55 2021 +0100
+++ b/src/HOL/Library/Multiset.thy Mon Mar 22 12:18:35 2021 +0000
@@ -2329,7 +2329,7 @@
end
-context ordered_cancel_comm_monoid_diff
+context cancel_comm_monoid_add
begin
lemma sum_mset_diff: