diff --git a/bin/sleep/sleep.c b/bin/sleep/sleep.c
index 34d335cf473..3be82dbd218 100644
--- a/bin/sleep/sleep.c
+++ b/bin/sleep/sleep.c
@@ -1,4 +1,6 @@
 /*-
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
  * Copyright (c) 1988, 1993, 1994
  *	The Regents of the University of California.  All rights reserved.
  *