diff --git a/src/util/random.cpp b/src/util/random.cpp
index 41775e4..f6722b9 100644
--- a/src/util/random.cpp
+++ b/src/util/random.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2013-2016 Regents of the University of California.
+/*
+ * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -48,7 +48,7 @@
 {
   if (RAND_bytes(bytes, size) != 1) {
     BOOST_THROW_EXCEPTION(std::runtime_error("Failed to generate random bytes (error code " +
-                                             std::to_string(ERR_get_error()) + ")"));
+                                             to_string(ERR_get_error()) + ")"));
   }
 }