diff --git a/lib/private/SystemTag/SystemTagObjectMapper.php b/lib/private/SystemTag/SystemTagObjectMapper.php
index e0eb68cfa1791..052921ecdf47b 100644
--- a/lib/private/SystemTag/SystemTagObjectMapper.php
+++ b/lib/private/SystemTag/SystemTagObjectMapper.php
@@ -292,8 +292,8 @@ function (ISystemTag $tag) {
 	 */
 	public function setObjectIdsForTag(string $tagId, string $objectType, array $objectIds): void {
 		$currentObjectIds = $this->getObjectIdsForTags($tagId, $objectType);
-		$removedObjectIds = array_diff($currentObjectIds, $objectIds);
-		$addedObjectIds = array_diff($objectIds, $currentObjectIds);
+		$removedObjectIds = array_values(array_diff($currentObjectIds, $objectIds));
+		$addedObjectIds = array_values(array_diff($objectIds, $currentObjectIds));
 
 		$this->connection->beginTransaction();
 		$query = $this->connection->getQueryBuilder();