diff --git a/apps/dav/lib/CalDAV/CalDavBackend.php b/apps/dav/lib/CalDAV/CalDavBackend.php
index d11453afd62..d0faf40106d 100644
--- a/apps/dav/lib/CalDAV/CalDavBackend.php
+++ b/apps/dav/lib/CalDAV/CalDavBackend.php
@@ -3097,7 +3097,9 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 		$query->select($query->func()->max('id'))
 			->from('calendarchanges');
 
-		$maxId =  $query->executeQuery()->fetchOne();
+		$result = $query->executeQuery();
+		$maxId = (int) $result->fetchOne();
+		$result->closeCursor();
 		if (!$maxId || $maxId < $keep) {
 		    return 0;
 		}
diff --git a/apps/dav/lib/CardDAV/CardDavBackend.php b/apps/dav/lib/CardDAV/CardDavBackend.php
index b6a24652016..f4e8243cb2f 100644
--- a/apps/dav/lib/CardDAV/CardDavBackend.php
+++ b/apps/dav/lib/CardDAV/CardDavBackend.php
@@ -1328,7 +1328,9 @@ class CardDavBackend implements BackendInterface, SyncSupport {
 		$query->select($query->func()->max('id'))
 			->from('addressbookchanges');
 
-		$maxId =  $query->executeQuery()->fetchOne();
+		$result = $query->executeQuery();
+		$maxId = (int) $result->fetchOne();
+		$result->closeCursor();
 		if (!$maxId || $maxId < $keep) {
 		    return 0;
 		}