diff --git a/packages/backend/src/core/note/NoteMutingService.ts b/packages/backend/src/core/note/NoteMutingService.ts
index f63d2c4765..55d3cdcc25 100644
--- a/packages/backend/src/core/note/NoteMutingService.ts
+++ b/packages/backend/src/core/note/NoteMutingService.ts
@@ -1,3 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
 import { Inject, Injectable, OnApplicationShutdown } from '@nestjs/common';
 import * as Redis from 'ioredis';
 import { RedisKVCache } from '@/misc/cache.js';