diff --git a/src/input/rs232.c b/src/input/rs232.c
index 9da01a3..c801ab2 100644
--- a/src/input/rs232.c
+++ b/src/input/rs232.c
@@ -7,6 +7,8 @@
  * Authors:	Harald Welte <laforge@gnumonks.org>
  *		Pablo Neira Ayuso <pablo@gnumonks.org>
  *
+ * 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