diff --git a/Transceiver52M/radioClock.cpp b/Transceiver52M/radioClock.cpp
index 505bb01..2befd0d 100644
--- a/Transceiver52M/radioClock.cpp
+++ b/Transceiver52M/radioClock.cpp
@@ -4,6 +4,8 @@
  *
  * Copyright 2011 Free Software Foundation, Inc.
  *
+ * SPDX-License-Identifier: AGPL-3.0+
+ *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as published by
  * the Free Software Foundation, either version 3 of the License, or