diff --git a/apps/dav/lib/CalDAV/Schedule/Plugin.php b/apps/dav/lib/CalDAV/Schedule/Plugin.php
index 40f3726912367..0adc520a443a2 100644
--- a/apps/dav/lib/CalDAV/Schedule/Plugin.php
+++ b/apps/dav/lib/CalDAV/Schedule/Plugin.php
@@ -757,7 +757,7 @@ private function handleSameOrganizerException(
 
 		$addresses = $this->getAddressesForPrincipal($calendarNode->getOwner());
 		foreach ($vCal->VEVENT as $vevent) {
-			if (in_array($vevent->ORGANIZER->getNormalizedValue(), $addresses, true)) {
+			if (isset($vevent->ORGANIZER) && in_array($vevent->ORGANIZER->getNormalizedValue(), $addresses, true)) {
 				// User is an organizer => throw the exception
 				throw $e;
 			}