diff --git a/adler32.c b/adler32.c
index 04b81d29b..d1bb34dde 100644
--- a/adler32.c
+++ b/adler32.c
@@ -1,6 +1,7 @@
 /* adler32.c -- compute the Adler-32 checksum of a data stream
  * Copyright (C) 1995-2011, 2016 Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
+ * SPDX-License-Identifier: Zlib
  */
 
 /* @(#) $Id$ */
diff --git a/zlib.h b/zlib.h
index 0a9e7909f..49fe522ac 100644
--- a/zlib.h
+++ b/zlib.h
@@ -26,6 +26,7 @@
   The data format used by the zlib library is described by RFCs (Request for
   Comments) 1950 to 1952 at https://datatracker.ietf.org/doc/html/rfc1950
   (zlib format), rfc1951 (deflate format) and rfc1952 (gzip format).
+  SPDX-License-Identifier: Zlib
 */
 
 #ifndef ZLIB_H