diff --git a/programs/pkey/pk_sign.c b/programs/pkey/pk_sign.c
index f847e3f..151e263 100644
--- a/programs/pkey/pk_sign.c
+++ b/programs/pkey/pk_sign.c
@@ -3,7 +3,7 @@
  *
  *  Copyright (C) 2006-2013, ARM Limited, All Rights Reserved
  *
- *  This file is part of mbed TLS (http://www.polarssl.org)
+ *  This file is part of mbed TLS (https://www.polarssl.org)
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by