diff --git a/addons/purchase/purchase.py b/addons/purchase/purchase.py
index 34b6fec6cca..ffdda3b1829 100644
--- a/addons/purchase/purchase.py
+++ b/addons/purchase/purchase.py
@@ -58,15 +58,14 @@ class purchase_order(osv.osv):
         if not value: return False
         if type(ids)!=type([]):
             ids=[ids]
+        pol_obj = self.pool.get('purchase.order.line')
         for po in self.browse(cr, uid, ids, context=context):
             if po.order_line:
-                cr.execute("""update purchase_order_line set
-                        date_planned=%s
-                    where
-                        order_id=%s and
-                        (date_planned=%s or date_planned<%s)""", (value,po.id,po.minimum_planned_date,value))
-            cr.execute("""update purchase_order set
-                    minimum_planned_date=%s where id=%s""", (value, po.id))
+                pol_ids = pol_obj.search(cr, uid, [
+                    ('order_id', '=', po.id), '|', ('date_planned', '=', po.minimum_planned_date), ('date_planned', '<', value)
+                ], context=context)
+                pol_obj.write(cr, uid, pol_ids, {'date_planned': value}, context=context)
+                self.pool.get('purchase.order').write(cr, uid, po.id, {'minimum_planned_date': value}, context=context)
         self.invalidate_cache(cr, uid, context=context)
         return True