diff -r 304a47739407 -r 04ce6bb14d85 src/HOL/Finite_Set.thy
--- a/src/HOL/Finite_Set.thy	Thu Sep 24 19:14:18 2009 +0200
+++ b/src/HOL/Finite_Set.thy	Fri Sep 25 09:50:31 2009 +0200
@@ -1565,9 +1565,7 @@
   apply (rule finite_subset)
   prefer 2
   apply assumption
-  apply auto
-  apply (rule setsum_cong)
-  apply auto
+  apply (auto simp add: sup_absorb2)
 done
 
 lemma setsum_right_distrib: