diff --git a/wcs/forms/backoffice.py b/wcs/forms/backoffice.py
index 3c4a377e5..9ed615975 100644
--- a/wcs/forms/backoffice.py
+++ b/wcs/forms/backoffice.py
@@ -166,11 +166,8 @@ class FormDefUI(object):
             order_by = None
         if order_by and not anonymise:
             ordered_ids = formdata_class.get_sorted_ids(order_by)
-            new_item_ids = []
-            for item_id in ordered_ids:
-                if item_id in item_ids:
-                    new_item_ids.append(item_id)
-            item_ids = new_item_ids
+            item_ids_dict = {x: True for x in item_ids}
+            item_ids = [x for x in ordered_ids if x in item_ids_dict]
         else:
             item_ids.sort(lambda x,y: cmp(int(x), int(y)))
             item_ids.reverse()