diff --git a/CommonLibs/Interthread.h b/CommonLibs/Interthread.h
index 185112f..8169985 100644
--- a/CommonLibs/Interthread.h
+++ b/CommonLibs/Interthread.h
@@ -1,6 +1,8 @@
 /*
 * Copyright 2008, 2011 Free Software Foundation, Inc.
 *
+* SPDX-License-Identifier: AGPL-3.0+
+*
 * This software is distributed under the terms of the GNU Affero Public License.
 * See the COPYING file in the main directory for details.
 *