diff --git a/addons/calendar/calendar.py b/addons/calendar/calendar.py
index 43064b369d6..b1644c64edd 100644
--- a/addons/calendar/calendar.py
+++ b/addons/calendar/calendar.py
@@ -1197,6 +1197,7 @@ class calendar_event(osv.Model):
                 # check if there are one False
                 pile = []
                 ok = True
+                r_date = None
                 for arg in domain:
                     if str(arg[0]) in ('start', 'stop', 'final_date'):
                         if str(arg[0]) == 'start':