diff --git a/account.py b/account.py
index c5310fd..3312239 100644
--- a/account.py
+++ b/account.py
@@ -4,6 +4,7 @@ from trytond.i18n import gettext
 from trytond.model import ModelView
 
 from decimal import Decimal
+from itertools import groupby
 
 
 __all__ = ['Account','Move','Line']