diff --git a/addons/calendar/calendar.py b/addons/calendar/calendar.py
index 6162d3cb8cf..f0862601611 100644
--- a/addons/calendar/calendar.py
+++ b/addons/calendar/calendar.py
@@ -2,7 +2,7 @@
 ##############################################################################
 #
 #    OpenERP, Open Source Business Applications
-#    Copyright (c) 2011 OpenERP S.A. <http://openerp.com>
+#    Copyright (c) 2011-2014 OpenERP S.A. <http://openerp.com>
 #
 #    This program is free software: you can redistribute it and/or modify
 #    it under the terms of the GNU Affero General Public License as
@@ -831,7 +831,7 @@ class calendar_event(osv.Model):
         'fr': fields.boolean('Fri'),
         'sa': fields.boolean('Sat'),
         'su': fields.boolean('Sun'),
-        'month_by': fields.selection([('date', 'Date of month'), ('day', 'Day of month')], 'Option'),
+        'month_by': fields.selection([('date', 'Date of month'), ('day', 'Day of month')], 'Option', oldname='select1'),
         'day': fields.integer('Date of month'),
         'week_list': fields.selection([('MO', 'Monday'), ('TU', 'Tuesday'), ('WE', 'Wednesday'), ('TH', 'Thursday'), ('FR', 'Friday'), ('SA', 'Saturday'), ('SU', 'Sunday')], 'Weekday'),
         'byday': fields.selection([('1', 'First'), ('2', 'Second'), ('3', 'Third'), ('4', 'Fourth'), ('5', 'Fifth'), ('-1', 'Last')], 'By day'),