diff --git a/tryton/gui/window/form.py b/tryton/gui/window/form.py
index a92b6be160..7c9c60db41 100644
--- a/tryton/gui/window/form.py
+++ b/tryton/gui/window/form.py
@@ -22,6 +22,7 @@ import pango
 from tryton.translate import date_format
 from tryton.common import DT_FORMAT, DHM_FORMAT, HM_FORMAT
 import mx.DateTime
+import datetime as DT
 
 _ = gettext.gettext