diff --git a/include/libtorrent/aux_/session_impl.hpp b/include/libtorrent/aux_/session_impl.hpp
index cd148c020..96795c0d9 100644
--- a/include/libtorrent/aux_/session_impl.hpp
+++ b/include/libtorrent/aux_/session_impl.hpp
@@ -176,6 +176,7 @@ namespace libtorrent
 			void start_dht(entry const& startup_state);
 			void stop_dht();
 			entry dht_state() const;
+			void maybe_update_udp_mapping(int nat, int local_port, int external_port);
 #endif
 
 #ifndef TORRENT_DISABLE_ENCRYPTION
diff --git a/include/libtorrent/natpmp.hpp b/include/libtorrent/natpmp.hpp
index eac46b3d0..000c1aa99 100644
--- a/include/libtorrent/natpmp.hpp
+++ b/include/libtorrent/natpmp.hpp
@@ -63,6 +63,7 @@ public:
 	enum protocol_type { none = 0, udp = 1, tcp = 2 };
 	int add_mapping(protocol_type p, int external_port, int local_port);
 	void delete_mapping(int mapping_index);
+	bool get_mapping(int mapping_index, int& local_port, int& external_port, int& protocol) const;
 
 	void close();
 
@@ -88,6 +89,7 @@ private:
 			, local_port(0)
 			, external_port(0)
 			, protocol(none)
+			, map_sent(false)
 		{}
 
 		// indicates that the mapping has changed
@@ -107,6 +109,9 @@ private:
 		int external_port;
 
 		int protocol;
+
+		// set to true when the first map request is sent
+		bool map_sent;
 	};
 
 	portmap_callback_t m_callback;
diff --git a/include/libtorrent/upnp.hpp b/include/libtorrent/upnp.hpp
index c82bb3232..f0368196c 100644
--- a/include/libtorrent/upnp.hpp
+++ b/include/libtorrent/upnp.hpp
@@ -79,6 +79,7 @@ public:
 	enum protocol_type { none = 0, udp = 1, tcp = 2 };
 	int add_mapping(protocol_type p, int external_port, int local_port);
 	void delete_mapping(int mapping_index);
+	bool get_mapping(int mapping_index, int& local_port, int& external_port, int& protocol) const;
 
 	void discover_device();
 	void close();
diff --git a/src/natpmp.cpp b/src/natpmp.cpp
index 77b03e562..80af9af8a 100644
--- a/src/natpmp.cpp
+++ b/src/natpmp.cpp
@@ -114,6 +114,18 @@ void natpmp::rebind(address const& listen_interface)
 	}
 }
 
+bool natpmp::get_mapping(int index, int& local_port, int& external_port, int& protocol) const
+{
+	TORRENT_ASSERT(index < int(m_mappings.size()) && index >= 0);
+	if (index >= int(m_mappings.size()) || index < 0) return false;
+	mapping_t const& m = m_mappings[index];
+	if (m.protocol == none) return false;
+	local_port = m.local_port;
+	external_port = m.external_port;
+	protocol = m.protocol;
+	return true;
+}
+
 void natpmp::log(std::string const& msg)
 {
 	m_callback(-1, 0, msg);
@@ -132,6 +144,7 @@ void natpmp::disable(char const* message)
 	}
 	close();
 }
+
 void natpmp::delete_mapping(int index)
 {
 	TORRENT_ASSERT(index < int(m_mappings.size()) && index >= 0);
@@ -139,6 +152,12 @@ void natpmp::delete_mapping(int index)
 	mapping_t& m = m_mappings[index];
 
 	if (m.protocol == none) return;
+	if (!m.map_sent)
+	{
+		m.action = mapping_t::action_none;
+		m.protocol = none;
+		return;
+	}
 
 	m.action = mapping_t::action_delete;
 	update_mapping(index);
@@ -270,7 +289,7 @@ void natpmp::send_map_request(int i)
 	write_uint32(ttl, out); // port mapping lifetime
 
 	std::stringstream msg;
-	msg << "port map [ action: " << (m.action == mapping_t::action_add ? "add" : "delete")
+	msg << "==> port map [ action: " << (m.action == mapping_t::action_add ? "add" : "delete")
 		<< " proto: " << (m.protocol == udp ? "udp" : "tcp")
 		<< " local: " << m.local_port << " external: " << m.external_port
 		<< " ttl: " << ttl << " ]";
@@ -278,6 +297,7 @@ void natpmp::send_map_request(int i)
 
 	error_code ec;
 	m_socket.send_to(asio::buffer(buf, 12), m_nat_endpoint, 0, ec);
+	m.map_sent = true;
 	// linear back-off instead of exponential
 	++m_retry_count;
 	m_send_timer.expires_from_now(milliseconds(250 * m_retry_count), ec);
@@ -348,7 +368,7 @@ void natpmp::on_reply(error_code const& e
 	(void)time; // to remove warning
 
 	std::stringstream msg;
-	msg << "port map ["
+	msg << "<== port map ["
 		<< " protocol: " << (cmd - 128 == 1 ? "udp" : "tcp")
 		<< " local: " << private_port << " external: " << public_port
 		<< " ttl: " << lifetime << " ]";
@@ -486,7 +506,7 @@ void natpmp::close()
 {
 	mutex_t::scoped_lock l(m_mutex);
 	m_abort = true;
-	error_code ec;
+	log("closing");
 /*
 #if defined(TORRENT_LOGGING) || defined(TORRENT_VERBOSE_LOGGING)
 	m_log << time_now_string() << " close" << std::endl;
@@ -511,6 +531,7 @@ void natpmp::close()
 		if (i->protocol == none) continue;
 		i->action = mapping_t::action_delete;
 	}
+	error_code ec;
 	m_refresh_timer.cancel(ec);
 	update_mapping(0);
 }
diff --git a/src/session_impl.cpp b/src/session_impl.cpp
index a3616555b..e1a479e9e 100644
--- a/src/session_impl.cpp
+++ b/src/session_impl.cpp
@@ -1990,20 +1990,9 @@ namespace aux {
 				m_dht_settings.service_port = new_interface.port();
 			// the listen interface changed, rebind the dht listen socket as well
 			m_dht_socket.bind(m_dht_settings.service_port);
-			if (m_natpmp.get())
-			{
-				if (m_udp_mapping[0] != -1) m_natpmp->delete_mapping(m_udp_mapping[0]);
-				m_udp_mapping[0] = m_natpmp->add_mapping(natpmp::tcp
-					, m_dht_settings.service_port
-					, m_dht_settings.service_port);
-			}
-			if (m_upnp.get())
-			{
-				if (m_udp_mapping[1] != -1) m_upnp->delete_mapping(m_udp_mapping[1]);
-				m_udp_mapping[1] = m_upnp->add_mapping(upnp::tcp
-					, m_dht_settings.service_port
-					, m_dht_settings.service_port);
-			}
+
+			maybe_update_udp_mapping(0, m_dht_settings.service_port, m_dht_settings.service_port);
+			maybe_update_udp_mapping(1, m_dht_settings.service_port, m_dht_settings.service_port);
 		}
 #endif
 
@@ -2194,18 +2183,8 @@ namespace aux {
 				m_dht_settings.service_port = 45000 + (rand() % 10000);
 		}
 		m_external_udp_port = m_dht_settings.service_port;
-		if (m_natpmp.get() && m_udp_mapping[0] == -1)
-		{
-			m_udp_mapping[0] = m_natpmp->add_mapping(natpmp::udp
-				, m_dht_settings.service_port
-				, m_dht_settings.service_port);
-		}
-		if (m_upnp.get() && m_udp_mapping[1] == -1)
-		{
-			m_udp_mapping[1] = m_upnp->add_mapping(upnp::udp
-				, m_dht_settings.service_port
-				, m_dht_settings.service_port);
-		}
+		maybe_update_udp_mapping(0, m_dht_settings.service_port, m_dht_settings.service_port);
+		maybe_update_udp_mapping(1, m_dht_settings.service_port, m_dht_settings.service_port);
 		m_dht = new dht::dht_tracker(*this, m_dht_socket, m_dht_settings, &startup_state);
 		if (!m_dht_socket.is_open() || m_dht_socket.local_port() != m_dht_settings.service_port)
 		{
@@ -2222,6 +2201,45 @@ namespace aux {
 		m_dht->start(startup_state);
 	}
 
+#ifndef TORRENT_DISABLE_DHT	
+	void session_impl::maybe_update_udp_mapping(int nat, int local_port, int external_port)
+	{
+		int local, external, protocol;
+		if (nat == 0 && m_natpmp.get())
+		{
+			if (m_udp_mapping[nat] != -1)
+			{
+				if (m_natpmp->get_mapping(m_udp_mapping[nat], local, external, protocol))
+				{
+					// we already have a mapping. If it's the same, don't do anything
+					if (local == local_port && external == external_port && protocol == natpmp::udp)
+						return;
+				}
+				m_natpmp->delete_mapping(m_udp_mapping[nat]);
+			}
+			m_udp_mapping[nat] = m_natpmp->add_mapping(natpmp::udp
+				, local_port, external_port);
+			return;
+		}
+		else if (nat == 1 && m_upnp.get())
+		{
+			if (m_udp_mapping[nat] != -1)
+			{
+				if (m_upnp->get_mapping(m_udp_mapping[nat], local, external, protocol))
+				{
+					// we already have a mapping. If it's the same, don't do anything
+					if (local == local_port && external == external_port && protocol == natpmp::udp)
+						return;
+				}
+				m_upnp->delete_mapping(m_udp_mapping[nat]);
+			}
+			m_udp_mapping[nat] = m_upnp->add_mapping(upnp::udp
+				, local_port, external_port);
+			return;
+		}
+	}
+#endif
+
 	void session_impl::stop_dht()
 	{
 		mutex_t::scoped_lock l(m_mutex);
@@ -2246,20 +2264,8 @@ namespace aux {
 		{
 			m_dht_socket.bind(settings.service_port);
 
-			if (m_natpmp.get())
-			{
-				if (m_udp_mapping[0] != -1) m_upnp->delete_mapping(m_udp_mapping[0]);
-				m_udp_mapping[0] = m_natpmp->add_mapping(natpmp::udp
-					, m_dht_settings.service_port
-					, m_dht_settings.service_port);
-			}
-			if (m_upnp.get())
-			{
-				if (m_udp_mapping[1] != -1) m_upnp->delete_mapping(m_udp_mapping[1]);
-				m_udp_mapping[1] = m_upnp->add_mapping(upnp::udp
-					, m_dht_settings.service_port
-					, m_dht_settings.service_port);
-			}
+			maybe_update_udp_mapping(0, settings.service_port, settings.service_port);
+			maybe_update_udp_mapping(1, settings.service_port, settings.service_port);
 			m_external_udp_port = settings.service_port;
 		}
 		m_dht_settings = settings;
diff --git a/src/upnp.cpp b/src/upnp.cpp
index 28eaae4c9..85941c7e7 100644
--- a/src/upnp.cpp
+++ b/src/upnp.cpp
@@ -228,6 +228,18 @@ void upnp::delete_mapping(int mapping)
 	}
 }
 
+bool upnp::get_mapping(int index, int& local_port, int& external_port, int& protocol) const
+{
+	TORRENT_ASSERT(index < int(m_mappings.size()) && index >= 0);
+	if (index >= int(m_mappings.size()) || index < 0) return false;
+	global_mapping_t const& m = m_mappings[index];
+	if (m.protocol == none) return false;
+	local_port = m.local_port;
+	external_port = m.external_port;
+	protocol = m.protocol;
+	return true;
+}
+
 void upnp::resend_request(error_code const& e)
 {
 	if (e) return;