diff --git a/apps/files_external/lib/Lib/Backend/SMB.php b/apps/files_external/lib/Lib/Backend/SMB.php
index 79c5e4dd55a8f..9e2e2dbf35741 100644
--- a/apps/files_external/lib/Lib/Backend/SMB.php
+++ b/apps/files_external/lib/Lib/Backend/SMB.php
@@ -70,7 +70,7 @@ public function manipulateStorageConfig(StorageConfig &$storage, ?IUser $user =
 
 			$smbAuth = new BasicAuth(
 				$storage->getBackendOption('user'),
-				$storage->getBackendOption('domain'),
+				$storage->getBackendOption('domain') ?: null,
 				$storage->getBackendOption('password')
 			);
 		} else {