diff --git a/library/SIP_Emulation.ttcn b/library/SIP_Emulation.ttcn
index 98f7371..e71c611 100644
--- a/library/SIP_Emulation.ttcn
+++ b/library/SIP_Emulation.ttcn
@@ -24,6 +24,8 @@
  *
  * 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 SIPmsg_Types all;