diff --git a/src/util/io.hpp b/src/util/io.hpp
index cad5a26..5a8034a 100644
--- a/src/util/io.hpp
+++ b/src/util/io.hpp
@@ -1,5 +1,5 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
+/*
  * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
@@ -25,7 +25,6 @@
 #include "concepts.hpp"
 #include "../encoding/block.hpp"
 
-#include <iostream>
 #include <fstream>
 
 namespace ndn {
diff --git a/src/util/time.cpp b/src/util/time.cpp
index 8452075..6f669cb 100644
--- a/src/util/time.cpp
+++ b/src/util/time.cpp
@@ -1,5 +1,5 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
+/*
  * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
@@ -23,6 +23,7 @@
 #include "time-custom-clock.hpp"
 
 #include <boost/date_time/posix_time/posix_time.hpp>
+#include <sstream>
 
 namespace ndn {
 namespace time {