diff --git a/include/mbedtls/error.h b/include/mbedtls/error.h
index 8b4d3a8..c7f6a72 100644
--- a/include/mbedtls/error.h
+++ b/include/mbedtls/error.h
@@ -4,7 +4,7 @@
  * \brief Error to string translation
  */
 /*
- *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  Copyright (C) 2006-2018, ARM Limited, All Rights Reserved
  *  SPDX-License-Identifier: Apache-2.0
  *
  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
@@ -88,6 +88,7 @@
  * RSA       4   11
  * ECP       4   9 (Started from top)
  * MD        5   5
+ * HKDF      5   1 (Started from top)
  * CIPHER    6   8
  * SSL       6   17 (Started from top)
  * SSL       7   31