diff --git a/doc/copyright.texi b/doc/copyright.texi
index 509b94a09..cae593578 100644
--- a/doc/copyright.texi
+++ b/doc/copyright.texi
@@ -88,6 +88,7 @@ The parts of the libroken, most of libtelnet, telnet, ftp,
 and popper.
 
 @verbatim
+SPDX-License-Identifier: BSD-3-Clause
 
 Copyright (c) 1988, 1990, 1993
      The Regents of the University of California.  All rights reserved.