diff --git a/ndn-cxx/transport/stream-transport-impl.hpp b/ndn-cxx/transport/detail/stream-transport-impl.hpp
similarity index 97%
rename from ndn-cxx/transport/stream-transport-impl.hpp
rename to ndn-cxx/transport/detail/stream-transport-impl.hpp
index a36e6da..dda33e9 100644
--- a/ndn-cxx/transport/stream-transport-impl.hpp
+++ b/ndn-cxx/transport/detail/stream-transport-impl.hpp
@@ -19,8 +19,8 @@
  * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
  */
 
-#ifndef NDN_TRANSPORT_STREAM_TRANSPORT_IMPL_HPP
-#define NDN_TRANSPORT_STREAM_TRANSPORT_IMPL_HPP
+#ifndef NDN_TRANSPORT_DETAIL_STREAM_TRANSPORT_IMPL_HPP
+#define NDN_TRANSPORT_DETAIL_STREAM_TRANSPORT_IMPL_HPP
 
 #include "ndn-cxx/transport/transport.hpp"
 
@@ -30,6 +30,7 @@
 #include <list>
 
 namespace ndn {
+namespace detail {
 
 /** \brief Implementation detail of a Boost.Asio-based stream-oriented transport.
  *  \tparam BaseTransport a subclass of Transport
@@ -278,6 +279,7 @@
   boost::asio::deadline_timer m_connectTimer;
 };
 
+} // namespace detail
 } // namespace ndn
 
-#endif // NDN_TRANSPORT_STREAM_TRANSPORT_IMPL_HPP
+#endif // NDN_TRANSPORT_DETAIL_STREAM_TRANSPORT_IMPL_HPP
diff --git a/ndn-cxx/transport/stream-transport-with-resolver-impl.hpp b/ndn-cxx/transport/detail/stream-transport-with-resolver-impl.hpp
similarity index 90%
rename from ndn-cxx/transport/stream-transport-with-resolver-impl.hpp
rename to ndn-cxx/transport/detail/stream-transport-with-resolver-impl.hpp
index ec17ddb..6ca3b1e 100644
--- a/ndn-cxx/transport/stream-transport-with-resolver-impl.hpp
+++ b/ndn-cxx/transport/detail/stream-transport-with-resolver-impl.hpp
@@ -19,12 +19,13 @@
  * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
  */
 
-#ifndef NDN_TRANSPORT_STREAM_TRANSPORT_WITH_RESOLVER_IMPL_HPP
-#define NDN_TRANSPORT_STREAM_TRANSPORT_WITH_RESOLVER_IMPL_HPP
+#ifndef NDN_TRANSPORT_DETAIL_STREAM_TRANSPORT_WITH_RESOLVER_IMPL_HPP
+#define NDN_TRANSPORT_DETAIL_STREAM_TRANSPORT_WITH_RESOLVER_IMPL_HPP
 
-#include "ndn-cxx/transport/stream-transport-impl.hpp"
+#include "ndn-cxx/transport/detail/stream-transport-impl.hpp"
 
 namespace ndn {
+namespace detail {
 
 /** \brief implementation detail of a Boost.Asio-based stream-oriented transport
  *         with resolver support
@@ -88,7 +89,7 @@
   }
 };
 
-
+} // namespace detail
 } // namespace ndn
 
-#endif // NDN_TRANSPORT_STREAM_TRANSPORT_WITH_RESOLVER_IMPL_HPP
+#endif // NDN_TRANSPORT_DETAIL_STREAM_TRANSPORT_WITH_RESOLVER_IMPL_HPP
diff --git a/ndn-cxx/transport/tcp-transport.cpp b/ndn-cxx/transport/tcp-transport.cpp
index 34bcf28..30a5087 100644
--- a/ndn-cxx/transport/tcp-transport.cpp
+++ b/ndn-cxx/transport/tcp-transport.cpp
@@ -20,7 +20,7 @@
  */
 
 #include "ndn-cxx/transport/tcp-transport.hpp"
-#include "ndn-cxx/transport/stream-transport-with-resolver-impl.hpp"
+#include "ndn-cxx/transport/detail/stream-transport-with-resolver-impl.hpp"
 #include "ndn-cxx/net/face-uri.hpp"
 #include "ndn-cxx/util/logger.hpp"
 
diff --git a/ndn-cxx/transport/tcp-transport.hpp b/ndn-cxx/transport/tcp-transport.hpp
index 01d369c..e3bb5a3 100644
--- a/ndn-cxx/transport/tcp-transport.hpp
+++ b/ndn-cxx/transport/tcp-transport.hpp
@@ -29,12 +29,16 @@
 
 namespace ndn {
 
+namespace detail {
+
 template<typename BaseTransport, typename Protocol>
 class StreamTransportImpl;
 
 template<typename BaseTransport, typename Protocol>
 class StreamTransportWithResolverImpl;
 
+} // namespace detail
+
 /** \brief a transport using TCP socket
  */
 class TcpTransport : public Transport
@@ -77,8 +81,8 @@
   std::string m_host;
   std::string m_port;
 
-  using Impl = StreamTransportWithResolverImpl<TcpTransport, boost::asio::ip::tcp>;
-  friend class StreamTransportImpl<TcpTransport, boost::asio::ip::tcp>;
+  using Impl = detail::StreamTransportWithResolverImpl<TcpTransport, boost::asio::ip::tcp>;
+  friend class detail::StreamTransportImpl<TcpTransport, boost::asio::ip::tcp>;
   friend Impl;
   shared_ptr<Impl> m_impl;
 };
diff --git a/ndn-cxx/transport/unix-transport.cpp b/ndn-cxx/transport/unix-transport.cpp
index a107997..d444e35 100644
--- a/ndn-cxx/transport/unix-transport.cpp
+++ b/ndn-cxx/transport/unix-transport.cpp
@@ -20,7 +20,7 @@
  */
 
 #include "ndn-cxx/transport/unix-transport.hpp"
-#include "ndn-cxx/transport/stream-transport-impl.hpp"
+#include "ndn-cxx/transport/detail/stream-transport-impl.hpp"
 
 #include "ndn-cxx/face.hpp"
 #include "ndn-cxx/net/face-uri.hpp"
diff --git a/ndn-cxx/transport/unix-transport.hpp b/ndn-cxx/transport/unix-transport.hpp
index c78b015..424ed53 100644
--- a/ndn-cxx/transport/unix-transport.hpp
+++ b/ndn-cxx/transport/unix-transport.hpp
@@ -29,9 +29,13 @@
 
 namespace ndn {
 
+namespace detail {
+
 template<typename BaseTransport, typename Protocol>
 class StreamTransportImpl;
 
+} // namespace detail
+
 /** \brief a transport using Unix stream socket
  */
 class UnixTransport : public Transport
@@ -74,7 +78,7 @@
 private:
   std::string m_unixSocket;
 
-  using Impl = StreamTransportImpl<UnixTransport, boost::asio::local::stream_protocol>;
+  using Impl = detail::StreamTransportImpl<UnixTransport, boost::asio::local::stream_protocol>;
   friend Impl;
   shared_ptr<Impl> m_impl;
 };