diff --git a/addons/mail/mail_thread.py b/addons/mail/mail_thread.py
index 44c158cba01..a6060f5f54f 100644
--- a/addons/mail/mail_thread.py
+++ b/addons/mail/mail_thread.py
@@ -809,7 +809,7 @@ class mail_thread(osv.AbstractModel):
                     # as RFC2822 requires timezone offset in Date headers.
                     stored_date = parsed_date.replace(tzinfo=pytz.utc)
                 else:
-                    stored_date = parsed_date.astimezone(tzinfo=pytz.utc)
+                    stored_date = parsed_date.astimezone(tz=pytz.utc)
             except Exception:
                 _logger.warning('Failed to parse Date header %r in incoming mail '
                                 'with message-id %r, assuming current date/time.',