diff -urN zabbix-2.0.13.org/frontends/php/api/classes/CMaintenance.php zabbix-2.0.13.ZBX-8883/frontends/php/api/classes/CMaintenance.php
--- zabbix-2.0.13.org/frontends/php/api/classes/CMaintenance.php	2014-09-10 18:23:30.000000000 +0900
+++ zabbix-2.0.13.ZBX-8883/frontends/php/api/classes/CMaintenance.php	2014-10-10 21:54:56.000000000 +0900
@@ -209,12 +209,16 @@
 
 		// groupids
 		if (!is_null($options['groupids'])) {
-			$options['selectGroups'] = 1;
+			if (is_null($options['selectGroups'])) {
+				$options['selectGroups'] = API_OUTPUT_REFER;
+			}
 		}
 
 		// hostids
 		if (!is_null($options['hostids'])) {
-			$options['selectHosts'] = 1;
+			if (is_null($options['selectHosts'])) {
+				$options['selectHosts'] = API_OUTPUT_REFER;
+			}
 		}
 
 		// maintenanceids