diff --git a/lib/Mount/MountProvider.php b/lib/Mount/MountProvider.php
index 891f70438..9c566e5fc 100644
--- a/lib/Mount/MountProvider.php
+++ b/lib/Mount/MountProvider.php
@@ -307,7 +307,7 @@ public function getMountsForPath(string $setupPathHint, bool $forChildren, array
 				$loader,
 				$user,
 				$aclManager,
-				$folder->acl ? $aclManager->getRulesByFileIds([$folder->rootId]) : [],
+				$folder->acl ? $aclManager->getRulesByFileIds([$folder->rootId])[$folder->storageId] ?? [] : [],
 			);
 		}