diff --git a/src/util/dns.cpp b/src/util/dns.cpp
index 0adfbd2..73fd8b1 100644
--- a/src/util/dns.cpp
+++ b/src/util/dns.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2015 Regents of the University of California.
+ * Copyright (c) 2013-2016 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -20,9 +20,11 @@
  */
 
 #include "dns.hpp"
-
 #include "scheduler.hpp"
 
+#include <boost/asio/io_service.hpp>
+#include <boost/asio/ip/udp.hpp>
+
 namespace ndn {
 namespace dns {
 
diff --git a/src/util/dns.hpp b/src/util/dns.hpp
index 64d3865..fec923b 100644
--- a/src/util/dns.hpp
+++ b/src/util/dns.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2015 Regents of the University of California.
+ * Copyright (c) 2013-2016 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -25,7 +25,13 @@
 #include "../util/time.hpp"
 
 #include <boost/asio/ip/address.hpp>
-#include <boost/asio/io_service.hpp>
+
+// forward declaration
+namespace boost {
+namespace asio {
+class io_service;
+} // namespace asio
+} // namespace boost
 
 namespace ndn {
 namespace dns {
diff --git a/src/util/dummy-client-face.cpp b/src/util/dummy-client-face.cpp
index 1db5b8d..8cdb9dc 100644
--- a/src/util/dummy-client-face.cpp
+++ b/src/util/dummy-client-face.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2015 Regents of the University of California.
+ * Copyright (c) 2013-2016 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -24,6 +24,8 @@
 #include "../management/nfd-controller.hpp"
 #include "../management/nfd-control-response.hpp"
 
+#include <boost/asio/io_service.hpp>
+
 namespace ndn {
 namespace util {
 
diff --git a/src/util/monotonic_deadline_timer.hpp b/src/util/monotonic_deadline_timer.hpp
index 6572ca4..c2b28cf 100644
--- a/src/util/monotonic_deadline_timer.hpp
+++ b/src/util/monotonic_deadline_timer.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2014 Regents of the University of California.
+ * Copyright (c) 2013-2016 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -26,9 +26,10 @@
 #ifndef NDN_UTIL_MONOTONIC_DEADLINE_TIMER_HPP
 #define NDN_UTIL_MONOTONIC_DEADLINE_TIMER_HPP
 
-#include <boost/asio.hpp>
 #include "time.hpp"
 
+#include <boost/asio/basic_deadline_timer.hpp>
+
 namespace boost {
 namespace asio {
 
diff --git a/src/util/network-monitor.hpp b/src/util/network-monitor.hpp
index f3fc6b8..dae4941 100644
--- a/src/util/network-monitor.hpp
+++ b/src/util/network-monitor.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2015 Regents of the University of California.
+ * Copyright (c) 2013-2016 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -24,7 +24,12 @@
 
 #include "signal.hpp"
 
-#include <boost/asio/io_service.hpp>
+// forward declaration
+namespace boost {
+namespace asio {
+class io_service;
+} // namespace asio
+} // namespace boost
 
 namespace ndn {
 namespace util {