--- a/sql/item_sum.cc	2007-07-19 17:20:54.000000000 +0100
+++ b/sql/item_sum.cc	2007-09-08 18:53:21.000000000 +0100
@@ -3367,7 +3367,7 @@
   DBUG_ASSERT(fixed == 1);
   if (null_value)
     return 0;
-  if (!result.length() && tree)
+  if (no_appended && tree)
     /* Tree is used for sorting as in ORDER BY */
     tree_walk(tree, (tree_walk_action)&dump_leaf_key, (void*)this,
               left_root_right);