diff -r c61fe520602b -r 5018f6a76b3f src/HOL/Tools/record.ML
--- a/src/HOL/Tools/record.ML	Wed Oct 21 16:41:22 2009 +1100
+++ b/src/HOL/Tools/record.ML	Wed Oct 21 08:16:25 2009 +0200
@@ -1834,7 +1834,7 @@
     val extN = full bname;
     val types = map snd fields;
     val alphas_fields = fold Term.add_tfree_namesT types [];
-    val alphas_ext = alphas inter alphas_fields;
+    val alphas_ext = inter (op =) (alphas, alphas_fields);
     val len = length fields;
     val variants =
       Name.variant_list (moreN :: rN :: (rN ^ "'") :: wN :: parent_variants)