diff --git a/newlib/libc/include/sys/cdefs.h b/newlib/libc/include/sys/cdefs.h
index 49be9e062..c4cbef274 100644
--- a/newlib/libc/include/sys/cdefs.h
+++ b/newlib/libc/include/sys/cdefs.h
@@ -3,6 +3,8 @@
 /* Written 2000 by Werner Almesberger */
 
 /*-
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
  * Copyright (c) 1991, 1993
  *	The Regents of the University of California.  All rights reserved.
  *