diff --git a/include/libtorrent/udp_socket.hpp b/include/libtorrent/udp_socket.hpp
index 6dbc8cc36..2d39f00d1 100644
--- a/include/libtorrent/udp_socket.hpp
+++ b/include/libtorrent/udp_socket.hpp
@@ -147,7 +147,7 @@ namespace libtorrent
 		void wrap(char const* hostname, int port, char const* p, int len, error_code& ec);
 		void unwrap(error_code const& e, char const* buf, int size);
 
-		void maybe_realloc_buffers();
+		void maybe_realloc_buffers(int which = 3);
 
 #ifdef TORRENT_DEBUG
 #if defined BOOST_HAS_PTHREADS
@@ -168,12 +168,22 @@ namespace libtorrent
 		udp::endpoint m_v4_ep;
 		int m_v4_buf_size;
 		char* m_v4_buf;
+		// this is set to true to indicate that the
+		// m_v4_buf should be reallocated to the size
+		// of the buffer size members the next time their
+		// read handler gets triggered
+		bool m_reallocate_buffer4;
 
 #if TORRENT_USE_IPV6
 		udp::socket m_ipv6_sock;
 		udp::endpoint m_v6_ep;
 		int m_v6_buf_size;
 		char* m_v6_buf;
+		// this is set to true to indicate that the
+		// m_v6_buf should be reallocated to the size
+		// of the buffer size members the next time their
+		// read handler gets triggered
+		bool m_reallocate_buffer6;
 #endif
 
 		int m_bind_port;
@@ -188,11 +198,6 @@ namespace libtorrent
 		bool m_queue_packets;
 		bool m_tunnel_packets;
 		bool m_abort;
-		// this is set to true to indicate that the m_v4_buf
-		// and m_v6_buf should be reallocated to the size
-		// of the buffer size members the next time their
-		// read handler gets triggered
-		bool m_reallocate_buffers;
 		udp::endpoint m_proxy_addr;
 		// while we're connecting to the proxy
 		// we have to queue the packets, we'll flush
diff --git a/src/udp_socket.cpp b/src/udp_socket.cpp
index b58380c40..db410e402 100644
--- a/src/udp_socket.cpp
+++ b/src/udp_socket.cpp
@@ -61,10 +61,12 @@ udp_socket::udp_socket(asio::io_service& ios
 	, m_ipv4_sock(ios)
 	, m_v4_buf_size(0)
 	, m_v4_buf(0)
+	, m_reallocate_buffer4(false)
 #if TORRENT_USE_IPV6
 	, m_ipv6_sock(ios)
 	, m_v6_buf_size(0)
 	, m_v6_buf(0)
+	, m_reallocate_buffer6(false)
 #endif
 	, m_bind_port(0)
 	, m_outstanding(0)
@@ -75,7 +77,6 @@ udp_socket::udp_socket(asio::io_service& ios
 	, m_queue_packets(false)
 	, m_tunnel_packets(false)
 	, m_abort(false)
-	, m_reallocate_buffers(false)
 {
 #ifdef TORRENT_DEBUG
 	m_magic = 0x1337;
@@ -184,16 +185,20 @@ void udp_socket::send(udp::endpoint const& ep, char const* p, int len, error_cod
 #endif
 }
 
-void udp_socket::maybe_realloc_buffers()
+void udp_socket::maybe_realloc_buffers(int which)
 {
-	if (m_reallocate_buffers)
+	if (m_reallocate_buffer4 && (which & 1))
 	{
 		m_v4_buf = (char*)realloc(m_v4_buf, m_v4_buf_size);
-#if TORRENT_USE_IPV6
-		m_v6_buf = (char*)realloc(m_v6_buf, m_v6_buf_size);
-#endif
-		m_reallocate_buffers = false;
+		m_reallocate_buffer4 = false;
 	}
+#if TORRENT_USE_IPV6
+	if (m_reallocate_buffer6 && (which & 2))
+	{
+		m_v6_buf = (char*)realloc(m_v6_buf, m_v6_buf_size);
+		m_reallocate_buffer6 = false;
+	}
+#endif
 }
 
 void udp_socket::on_read(udp::socket* s, error_code const& e, std::size_t bytes_transferred)
@@ -221,6 +226,12 @@ void udp_socket::on_read(udp::socket* s, error_code const& e, std::size_t bytes_
 	CHECK_MAGIC;
 	if (!m_callback) return;
 
+#if TORRENT_USE_IPV6
+	int which = (s == &m_ipv4_sock) ? 1 : 2;
+#else
+	int which = 1;
+#endif
+
 	if (e)
 	{
 #ifndef BOOST_NO_EXCEPTIONS
@@ -259,7 +270,7 @@ void udp_socket::on_read(udp::socket* s, error_code const& e, std::size_t bytes_
 
 		if (m_abort) return;
 
-		maybe_realloc_buffers();
+		maybe_realloc_buffers(which);
 
 #if defined TORRENT_ASIO_DEBUGGING
 		add_outstanding_async("udp_socket::on_read");
@@ -308,7 +319,7 @@ void udp_socket::on_read(udp::socket* s, error_code const& e, std::size_t bytes_
 
 		if (m_abort) return;
 
-		maybe_realloc_buffers();
+		maybe_realloc_buffers(which);
 
 #if defined TORRENT_ASIO_DEBUGGING
 		add_outstanding_async("udp_socket::on_read");
@@ -340,7 +351,7 @@ void udp_socket::on_read(udp::socket* s, error_code const& e, std::size_t bytes_
 
 		if (m_abort) return;
 
-		maybe_realloc_buffers();
+		maybe_realloc_buffers(which);
 
 #if defined TORRENT_ASIO_DEBUGGING
 		add_outstanding_async("udp_socket::on_read");
@@ -505,10 +516,11 @@ void udp_socket::set_buf_size(int s)
 	if (s > m_v4_buf_size)
 	{
 		m_v4_buf_size = s;
+		m_reallocate_buffer4 = true;
 #if TORRENT_USE_IPV6
 		m_v6_buf_size = s;
+		m_reallocate_buffer6 = true;
 #endif
-		m_reallocate_buffers = true;
 	}
 }