diff --git a/addons/account/invoice.py b/addons/account/invoice.py
index f919f99cee7..514f9b2aceb 100644
--- a/addons/account/invoice.py
+++ b/addons/account/invoice.py
@@ -25,6 +25,7 @@ import decimal_precision as dp
 import netsvc
 from osv import fields, osv
 import ir
+from osv.orm import except_orm
 import pooler
 from tools import config
 from tools.translate import _