diff --git a/include/polarssl/ctr_drbg.h b/include/polarssl/ctr_drbg.h
index 26d76e5..b7984cb 100644
--- a/include/polarssl/ctr_drbg.h
+++ b/include/polarssl/ctr_drbg.h
@@ -5,7 +5,7 @@
  *
  *  Copyright (C) 2006-2014, 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