diff --git a/router/connection.go b/router/connection.go
index 1923621b..3a13a845 100644
--- a/router/connection.go
+++ b/router/connection.go
@@ -139,8 +139,8 @@ func (conn *LocalConnection) Shutdown(err error) {
 // Heartbeating serves two purposes: a) keeping NAT paths alive, and
 // b) updating a remote peer's knowledge of our address, in the event
 // it changes (e.g. because NAT paths expired).
-func (conn *LocalConnection) ReceivedHeartbeat(remoteUDPAddr *net.UDPAddr) {
-	if remoteUDPAddr == nil {
+func (conn *LocalConnection) ReceivedHeartbeat(remoteUDPAddr *net.UDPAddr, connUID uint64) {
+	if remoteUDPAddr == nil || connUID != conn.UID {
 		return
 	}
 	conn.queryChan <- &ConnectionInteraction{
@@ -176,10 +176,12 @@ func (conn *LocalConnection) run(queryChan <-chan *ConnectionInteraction, accept
 	}
 	log.Printf("->[%s] completed handshake with %s\n", conn.remoteTCPAddr, conn.remote.Name)
 
+	heartbeatFrameBytes := make([]byte, EthernetOverhead + 8)
+	binary.BigEndian.PutUint64(heartbeatFrameBytes[EthernetOverhead:], conn.UID)
 	conn.heartbeatFrame = &ForwardedFrame{
 		srcPeer: conn.local,
 		dstPeer: conn.remote,
-		frame:   []byte{}}
+		frame:   heartbeatFrameBytes}
 
 	go conn.receiveTCP(dec)
 	conn.Router.Ourself.AddConnection(conn)
diff --git a/router/consts.go b/router/consts.go
index 5bdd14f8..84baddd0 100644
--- a/router/consts.go
+++ b/router/consts.go
@@ -7,7 +7,7 @@ import (
 
 const (
 	Protocol           = "weave"
-	ProtocolVersion    = 9
+	ProtocolVersion    = 10
 	EthernetOverhead   = 14
 	UDPOverhead        = 28 // 20 bytes for IPv4, 8 bytes for UDP
 	Port               = 6783
diff --git a/router/router.go b/router/router.go
index c89b168b..aa0f05d7 100644
--- a/router/router.go
+++ b/router/router.go
@@ -247,7 +247,9 @@ func (router *Router) handleUDPPacketFunc(dec *EthernetDecoder, po PacketSink) F
 
 		dec.DecodeLayers(frame)
 		decodedLen := len(dec.decoded)
-
+		if decodedLen == 0 {
+			return nil
+		}
 		// Handle special frames produced internally (rather than
 		// captured/forwarded) by the remote router.
 		//
@@ -256,18 +258,19 @@ func (router *Router) handleUDPPacketFunc(dec *EthernetDecoder, po PacketSink) F
 		// efficient to do so, as we want to optimise for the common
 		// (i.e. non-special) frames. These always need decoding, and
 		// detecting special frames is cheaper post decoding than pre.
-		if decodedLen == 0 || (decodedLen == 1 && dec.IsSpecial()) {
+		if decodedLen == 1 && dec.IsSpecial() {
 			if srcPeer != relayConn.Remote() || dstPeer != router.Ourself.Peer {
 				// A special frame not originating from the remote, or
 				// not for us? How odd; let's just drop it.
 				return nil
 			}
-			if frameLen == 0 {
-				relayConn.ReceivedHeartbeat(sender)
-			} else if frameLen == FragTestSize && bytes.Equal(frame, FragTest) {
+			switch {
+			case frameLen == EthernetOverhead + 8:
+				relayConn.ReceivedHeartbeat(sender, binary.BigEndian.Uint64(frame[EthernetOverhead:]))
+			case frameLen == FragTestSize && bytes.Equal(frame, FragTest):
 				relayConn.SendTCP(ProtocolFragmentationReceivedByte)
-			} else if frameLen == PMTUDiscoverySize && bytes.Equal(frame, PMTUDiscovery) {
-			} else if decodedLen == 1 {
+			case frameLen == PMTUDiscoverySize && bytes.Equal(frame, PMTUDiscovery):
+			default:
 				frameLenBytes := []byte{0, 0}
 				binary.BigEndian.PutUint16(frameLenBytes, uint16(frameLen-EthernetOverhead))
 				relayConn.SendTCP(Concat(ProtocolPMTUVerifiedByte, frameLenBytes))