diff --git a/addons/hr_holidays/hr_holidays.py b/addons/hr_holidays/hr_holidays.py
index 1ff3ce1a510..aaff2183050 100644
--- a/addons/hr_holidays/hr_holidays.py
+++ b/addons/hr_holidays/hr_holidays.py
@@ -25,6 +25,7 @@ import datetime, time
 from itertools import groupby
 from operator import itemgetter
 
+import math
 import netsvc
 from osv import fields, osv
 from tools.translate import _