diff --git a/calendar/setup/setup.inc.php b/calendar/setup/setup.inc.php
index 7757ee4e0a..0d3d83a2f9 100755
--- a/calendar/setup/setup.inc.php
+++ b/calendar/setup/setup.inc.php
@@ -10,7 +10,7 @@
  */
 
 $setup_info['calendar']['name']    = 'calendar';
-$setup_info['calendar']['version'] = '1.9.009';
+$setup_info['calendar']['version'] = '1.9.010';
 $setup_info['calendar']['app_order'] = 3;
 $setup_info['calendar']['enable']  = 1;
 $setup_info['calendar']['index']   = 'calendar.calendar_uiviews.index';
diff --git a/calendar/setup/tables_current.inc.php b/calendar/setup/tables_current.inc.php
index c3b5058988..02cb10bb0f 100644
--- a/calendar/setup/tables_current.inc.php
+++ b/calendar/setup/tables_current.inc.php
@@ -38,7 +38,7 @@ $phpgw_baseline = array(
 		),
 		'pk' => array('cal_id'),
 		'fk' => array(),
-		'ix' => array('cal_uid','cal_owner','cal_modified','cal_deleted','caldav_name'),
+		'ix' => array('cal_uid','cal_owner','cal_modified','cal_reference','cal_deleted','caldav_name'),
 		'uc' => array()
 	),
 	'egw_cal_holidays' => array(
diff --git a/calendar/setup/tables_update.inc.php b/calendar/setup/tables_update.inc.php
index 6884788a15..f3a5924a2d 100644
--- a/calendar/setup/tables_update.inc.php
+++ b/calendar/setup/tables_update.inc.php
@@ -2238,10 +2238,20 @@ function calendar_upgrade1_9_008()
 	return $GLOBALS['setup_info']['calendar']['currentver'] = '1.9.009';
 }
 
+/**
+ * Create index on egw_cal.cal_reference to speed up etag generation of recuring events
+ */
+function calendar_upgrade1_9_009()
+{
+	$GLOBALS['egw_setup']->oProc->CreateIndex('egw_cal', array('cal_reference'));
+
+	return $GLOBALS['setup_info']['calendar']['currentver'] = '1.9.010';
+}
+
 /**
  * Add cal_rrule columns, drop egw_cal_repeats table
  */
-/*function calendar_upgrade1_9_009()
+/*function calendar_upgrade1_9_010()
 {
 	$GLOBALS['egw_setup']->oProc->AddColumn('egw_cal','cal_rrule',array(
 		'type' => 'varchar',
@@ -2266,6 +2276,6 @@ function calendar_upgrade1_9_008()
 	}
 	$GLOBALS['egw_setup']->oProc->DropTable('egw_cal_repeats');
 
-	return $GLOBALS['setup_info']['calendar']['currentver'] = '1.9.010';
+	return $GLOBALS['setup_info']['calendar']['currentver'] = '1.9.011';
 }
 */