diff --git a/calendar/inc/class.calendar_hooks.inc.php b/calendar/inc/class.calendar_hooks.inc.php
index 5041d9e10a..4467ee3151 100644
--- a/calendar/inc/class.calendar_hooks.inc.php
+++ b/calendar/inc/class.calendar_hooks.inc.php
@@ -407,7 +407,6 @@ class calendar_hooks
 				'help'		=> 'Default type of resources application selected in the calendar particpants research form.',
 				'xmlrpc'	=> True,
 				'admin'		=> False,
-				'forced'    => 'resources',
 				'default'	=> 'resources'
 			),
 			'default_private' => array(
diff --git a/calendar/setup/tables_update.inc.php b/calendar/setup/tables_update.inc.php
index 8615a017d9..585bfb6b2e 100644
--- a/calendar/setup/tables_update.inc.php
+++ b/calendar/setup/tables_update.inc.php
@@ -2730,5 +2730,8 @@ function calendar_upgrade16_1_001()
 	$GLOBALS['egw_setup']->oProc->AlterColumn('egw_cal_extra', 'cal_extra_value',
 		array('type' => 'varchar','meta' => 'cfvalue','precision' => '16384','nullable' => False,'default' => ''));
 
+	Api\Preferences::change_preference('calendar', 'defaultresource_sel', 'resources', 'addressbook', 'forced');
+	Api\Preferences::change_preference('calendar', 'defaultresource_sel', 'resources', 'addressbook', 'default');
+	
 	return $GLOBALS['setup_info']['calendar']['currentver'] = '16.1.002';
 }