diff --git a/newlib/libc/include/sys/tree.h b/newlib/libc/include/sys/tree.h
index f4167c4e4..aef934a10 100644
--- a/newlib/libc/include/sys/tree.h
+++ b/newlib/libc/include/sys/tree.h
@@ -3,6 +3,8 @@
 /* $FreeBSD$ */
 
 /*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * All rights reserved.
  *