diff --git a/apps/files_external/lib/Service/MountCacheService.php b/apps/files_external/lib/Service/MountCacheService.php
index 51244fa464f5c..12885694d7ac7 100644
--- a/apps/files_external/lib/Service/MountCacheService.php
+++ b/apps/files_external/lib/Service/MountCacheService.php
@@ -119,7 +119,7 @@ private function getCacheEntryForRoot(IUser $user, StorageConfig $storage): ICac
 		$data = [
 			'path' => '',
 			'path_hash' => md5(''),
-			'size' => 0,
+			'size' => -1,
 			'unencrypted_size' => 0,
 			'mtime' => 0,
 			'mimetype' => ICacheEntry::DIRECTORY_MIMETYPE,