diff --git a/addons/mrp/stock.py b/addons/mrp/stock.py
index 3b29e5e9b2d..bc19d3717eb 100644
--- a/addons/mrp/stock.py
+++ b/addons/mrp/stock.py
@@ -188,7 +188,7 @@ class StockMove(osv.osv):
                 production_obj.signal_workflow(cr, uid, [prod_id], 'button_produce')
             if move.production_id.id:
                 self.write(cr, uid, new_moves, {'production_id': move.production_id.id}, context=context)
-            res.append(new_moves)
+            res += new_moves
         return res
 
     def write(self, cr, uid, ids, vals, context=None):