diff --git a/apps/dav/lib/CalDAV/Status/StatusService.php b/apps/dav/lib/CalDAV/Status/StatusService.php
index 24e929f9d0e73..9dccd4e77a3fb 100644
--- a/apps/dav/lib/CalDAV/Status/StatusService.php
+++ b/apps/dav/lib/CalDAV/Status/StatusService.php
@@ -106,8 +106,7 @@ public function processCalendarStatus(string $userId): void {
 			if (isset($component['DTSTART']) && $userStatusTimestamp !== null) {
 				/** @var DateTimeImmutable $dateTime */
 				$dateTime = $component['DTSTART'][0];
-				$timestamp = $dateTime->getTimestamp();
-				if($userStatusTimestamp > $timestamp) {
+				if($dateTime instanceof DateTimeImmutable && $userStatusTimestamp > $dateTime->getTimestamp()) {
 					return false;
 				}
 			}