diff --git a/library/RSL_Emulation.ttcn b/library/RSL_Emulation.ttcn
index cdeca74..790dd7a 100644
--- a/library/RSL_Emulation.ttcn
+++ b/library/RSL_Emulation.ttcn
@@ -21,6 +21,8 @@
  *
  * Released under the terms of GNU General Public License, Version 2 or
  * (at your option) any later version.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
 import from Misc_Helpers all;