diff --git a/addons/google_calendar/google_calendar.py b/addons/google_calendar/google_calendar.py
index 340191e8cbf..e9debc8f1bb 100644
--- a/addons/google_calendar/google_calendar.py
+++ b/addons/google_calendar/google_calendar.py
@@ -236,12 +236,12 @@ class google_calendar(osv.AbstractModel):
             "start": {
                 type: start_date,
                 vstype: None,
-                'timeZone': context.get('tz', 'UTC'),
+                'timeZone': context.get('tz') or 'UTC',
             },
             "end": {
                 type: final_date,
                 vstype: None,
-                'timeZone': context.get('tz', 'UTC'),
+                'timeZone': context.get('tz') or 'UTC',
             },
             "attendees": attendee_list,
             "reminders": {