diff --git a/src/utp_stream.cpp b/src/utp_stream.cpp
index ff53ee193..e305296c5 100644
--- a/src/utp_stream.cpp
+++ b/src/utp_stream.cpp
@@ -315,6 +315,8 @@ struct utp_socket_impl
 		, m_stalled(false)
 		, m_confirmed(false)
 	{
+		TORRENT_ASSERT((m_recv_id == ((m_send_id + 1) & 0xffff))
+			|| (m_send_id == ((m_recv_id + 1) & 0xffff)));
 		m_sm->inc_stats_counter(counters::num_utp_idle);
 		TORRENT_ASSERT(m_userdata);
 		for (int i = 0; i != num_delay_hist; ++i)
@@ -2712,10 +2714,18 @@ bool utp_socket_impl::incoming_packet(boost::uint8_t const* buf, int size
 {
 	INVARIANT_CHECK;
 
-	utp_header const* ph = reinterpret_cast<utp_header const*>(buf);
-
 	m_sm->inc_stats_counter(counters::utp_packets_in);
 
+	if (size < sizeof(utp_header))
+	{
+		UTP_LOG("%8p: ERROR: incoming packet size too small:%d (ignored)\n"
+			, static_cast<void*>(this), size);
+		m_sm->inc_stats_counter(counters::utp_invalid_pkts_in);
+		return false;
+	}
+
+	utp_header const* ph = reinterpret_cast<utp_header const*>(buf);
+
 	if (ph->get_version() != 1)
 	{
 		UTP_LOG("%8p: ERROR: incoming packet version:%d (ignored)\n"
@@ -3105,7 +3115,14 @@ bool utp_socket_impl::incoming_packet(boost::uint8_t const* buf, int size
 				UTP_LOGV("%8p: received ST_SYN state:%s seq_nr:%d ack_nr:%d\n"
 					, static_cast<void*>(this), socket_state_names[m_state], m_seq_nr, m_ack_nr);
 #endif
-				TORRENT_ASSERT(m_send_id == ph->connection_id);
+				if (m_send_id != ph->connection_id)
+				{
+#if TORRENT_UTP_LOG
+					UTP_LOGV("%8p: received invalid connection_id:%d expected: %d\n"
+						, static_cast<void*>(this), int(ph->connection_id), int(m_send_id));
+#endif
+					return false;
+				}
 				TORRENT_ASSERT(m_recv_id == ((m_send_id + 1) & 0xffff));
 
 				defer_ack();