diff --git a/addons/crm/crm_calendar.py b/addons/crm/crm_calendar.py
index 5f42a80c7b8..a1bad20948c 100644
--- a/addons/crm/crm_calendar.py
+++ b/addons/crm/crm_calendar.py
@@ -358,6 +358,8 @@ class crm_case(osv.osv):
             ids = map(lambda x:int(str(x).split('-')[0]), ids)
         res = super(crm_case, self).read(cr, uid, ids, fields=fields, context=context, load=load)
         read_ids = ",".join([str(x) for x in ids])
+        if not read_ids:
+            return []
         cr.execute('select id,rrule,rdates from crm_case where id in (%s)' % read_ids)
         rrules = filter(lambda x: not x['rrule']==None, cr.dictfetchall())
         rdates = []