diff --git a/plugins/calendar/calendar.php b/plugins/calendar/calendar.php
index fce626a4..9089383a 100644
--- a/plugins/calendar/calendar.php
+++ b/plugins/calendar/calendar.php
@@ -603,8 +603,8 @@ class calendar extends rcube_plugin
       $json[] = array(
         'start' => date('c', $event['start']), // ISO 8601 date (added in PHP 5)
         'end'   => date('c', $event['end']), // ISO 8601 date (added in PHP 5)
-        'description' => $event['description'],
-        'location'    => $event['location'],
+        'description' => strval($event['description']),
+        'location'    => strval($event['location']),
         'className'   => ($addcss ? 'fc-event-cal-'.asciiwords($event['calendar'], true).' ' : '') . 'cat-' . asciiwords($event['categories'], true),
         'allDay'      => ($event['all_day'] == 1)?true:false,
       ) + $event;
diff --git a/plugins/calendar/drivers/kolab/kolab_calendar.php b/plugins/calendar/drivers/kolab/kolab_calendar.php
index 7610e6e9..7b23b2cf 100644
--- a/plugins/calendar/drivers/kolab/kolab_calendar.php
+++ b/plugins/calendar/drivers/kolab/kolab_calendar.php
@@ -322,8 +322,8 @@ class kolab_calendar
     return array(
       'id' => $rec['uid'],
       'uid' => $rec['uid'],
-      'title' => strval($rec['summary']),
-      'location' => strval($rec['location']),
+      'title' => $rec['summary'],
+      'location' => $rec['location'],
       'description' => $rec['body'],
       'start' => $rec['start-date'],
       'end' => $rec['end-date'],