diff --git a/addons/calendar/models/calendar_attendee.py b/addons/calendar/models/calendar_attendee.py
index f0009684ebd..a7d5f1ccd0d 100644
--- a/addons/calendar/models/calendar_attendee.py
+++ b/addons/calendar/models/calendar_attendee.py
@@ -118,6 +118,7 @@ class Attendee(models.Model):
                 event_id = attendee.event_id.id
                 ics_file = ics_files.get(event_id)
 
+                attachment_values = []
                 if ics_file:
                     attachment_values = [
                         (0, 0, {'name': 'invitation.ics',