diff --git a/addons/purchase/models/purchase.py b/addons/purchase/models/purchase.py
index 88faeee4001..398c2b61bee 100644
--- a/addons/purchase/models/purchase.py
+++ b/addons/purchase/models/purchase.py
@@ -324,8 +324,8 @@ class PurchaseOrder(models.Model):
     def button_approve(self, force=False):
         self.write({'state': 'purchase', 'date_approve': fields.Date.context_today(self)})
         self._create_picking()
-        if self.company_id.po_lock == 'lock':
-            self.write({'state': 'done'})
+        self.filtered(
+            lambda p: p.company_id.po_lock == 'lock').write({'state': 'done'})
         return {}
 
     @api.multi