diff --git a/bin/addons/base/module/module.py b/bin/addons/base/module/module.py
index 3dcd5b550c9..81985332157 100644
--- a/bin/addons/base/module/module.py
+++ b/bin/addons/base/module/module.py
@@ -53,7 +53,8 @@ class module_category(osv.osv):
         result = dict(cr.fetchall())
         for id in ids:
             cr.execute('select id from ir_module_category where parent_id=%s', (id,))
-            result[id] = reduce(lambda x,y:x+y, [result.get(c, 0) for (c,) in cr.fetchall()], result.get(id, 0))
+            result[id] = sum([result.get(c, 0) for (c,) in cr.fetchall()],
+                             result.get(id, 0))
         return result
 
     _columns = {