diff --git a/Transceiver52M/Resampler.cpp b/Transceiver52M/Resampler.cpp
index f545db8..7ba0219 100644
--- a/Transceiver52M/Resampler.cpp
+++ b/Transceiver52M/Resampler.cpp
@@ -2,6 +2,8 @@
  * Rational Sample Rate Conversion
  * Copyright (C) 2012, 2013  Thomas Tsou <tom@tsou.cc>
  *
+ * SPDX-License-Identifier: LGPL-2.1+
+ *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either