diff --git a/lib/kolab_sync_data_calendar.php b/lib/kolab_sync_data_calendar.php
--- a/lib/kolab_sync_data_calendar.php
+++ b/lib/kolab_sync_data_calendar.php
@@ -811,6 +811,7 @@
     {
         $emails = $this->user_emails();
 
+        $found = false;
         foreach ((array) $event['attendees'] as $i => $attendee) {
             if (!empty($attendee['email'])
                 && (empty($attendee['role']) || $attendee['role'] != 'ORGANIZER')
@@ -819,10 +820,11 @@
                 $event['attendees'][$i]['status'] = $status;
                 $event['attendees'][$i]['rsvp']   = false;
                 $event_attendee = $attendee;
+                $found = true;
             }
         }
 
-        if (empty($event_attendee)) {
+        if (!$found) {
             // Add the user to the attendees list
             $event['attendees'][] = array(
                 'role'   => 'OPT-PARTICIPANT',