diff --git a/lib/DAV/ACLPlugin.php b/lib/DAV/ACLPlugin.php
index caa99880a..3def992e4 100644
--- a/lib/DAV/ACLPlugin.php
+++ b/lib/DAV/ACLPlugin.php
@@ -93,7 +93,7 @@ public function propFind(PropFind $propFind, INode $node): void {
 			return;
 		}
 
-		$propFind->handle(self::ACL_LIST, function () use ($fileInfo, $mount): array {
+		$propFind->handle(self::ACL_LIST, function () use ($fileInfo, $mount): ?array {
 			$path = trim($mount->getSourcePath() . '/' . $fileInfo->getInternalPath(), '/');
 			if ($this->isAdmin($fileInfo->getPath())) {
 				$rules = $this->ruleManager->getAllRulesForPaths($mount->getNumericStorageId(), [$path]);