diff --git a/packages/backend/src/misc/distributed-lock.ts b/packages/backend/src/misc/distributed-lock.ts
index 0d7dfb1592..82375069ec 100644
--- a/packages/backend/src/misc/distributed-lock.ts
+++ b/packages/backend/src/misc/distributed-lock.ts
@@ -1,3 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
 import * as Redis from 'ioredis';
 
 export async function acquireDistributedLock(