diff -r 304a47739407 -r 04ce6bb14d85 src/HOL/Tools/Function/fundef_lib.ML
--- a/src/HOL/Tools/Function/fundef_lib.ML	Thu Sep 24 19:14:18 2009 +0200
+++ b/src/HOL/Tools/Function/fundef_lib.ML	Fri Sep 25 09:50:31 2009 +0200
@@ -170,7 +170,7 @@
  end
 
 (* instance for unions *)
-fun regroup_union_conv t = regroup_conv @{const_name Set.empty} @{const_name Set.union}
+fun regroup_union_conv t = regroup_conv @{const_name Set.empty} @{const_name Lattices.sup}
   (map (fn t => t RS eq_reflection) (@{thms Un_ac} @
                                      @{thms Un_empty_right} @
                                      @{thms Un_empty_left})) t