diff --git a/router/gossip.go b/router/gossip.go
index 9f1a30a4..78c2706b 100644
--- a/router/gossip.go
+++ b/router/gossip.go
@@ -20,13 +20,15 @@ type Gossip interface {
 	// specific message from one peer to another
 	// intermediate peers relay it using unicast topology.
 	GossipUnicast(dstPeerName PeerName, msg []byte) error
-	// send a message to every peer, relayed using broadcast topology.
-	GossipBroadcast(msg []byte) error
+	// send gossip to every peer, relayed using broadcast topology.
+	GossipBroadcast(update GossipData) error
 }
 
 type Gossiper interface {
 	OnGossipUnicast(sender PeerName, msg []byte) error
-	OnGossipBroadcast(msg []byte) error
+	// merge received data into state and return a representation of
+	// the received data, for further propagation
+	OnGossipBroadcast(update []byte) (GossipData, error)
 	// return state of everything we know; gets called periodically
 	Gossip() GossipData
 	// merge received data into state and return "everything new I've
@@ -150,15 +152,16 @@ func (c *GossipChannel) deliverUnicast(srcName PeerName, origPayload []byte, dec
 	return c.gossiper.OnGossipUnicast(srcName, payload)
 }
 
-func (c *GossipChannel) deliverBroadcast(srcName PeerName, origPayload []byte, dec *gob.Decoder) error {
+func (c *GossipChannel) deliverBroadcast(srcName PeerName, _ []byte, dec *gob.Decoder) error {
 	var payload []byte
 	if err := dec.Decode(&payload); err != nil {
 		return err
 	}
-	if err := c.gossiper.OnGossipBroadcast(payload); err != nil {
+	data, err := c.gossiper.OnGossipBroadcast(payload)
+	if err != nil || data == nil {
 		return err
 	}
-	return c.relayBroadcast(srcName, origPayload)
+	return c.relayBroadcast(srcName, data)
 }
 
 func (c *GossipChannel) deliver(_ PeerName, _ []byte, dec *gob.Decoder) error {
@@ -214,8 +217,8 @@ func (c *GossipChannel) GossipUnicast(dstPeerName PeerName, msg []byte) error {
 	return c.relayUnicast(dstPeerName, GobEncode(c.hash, c.ourself.Name, dstPeerName, msg))
 }
 
-func (c *GossipChannel) GossipBroadcast(msg []byte) error {
-	return c.relayBroadcast(c.ourself.Name, GobEncode(c.hash, c.ourself.Name, msg))
+func (c *GossipChannel) GossipBroadcast(update GossipData) error {
+	return c.relayBroadcast(c.ourself.Name, update)
 }
 
 func (c *GossipChannel) relayUnicast(dstPeerName PeerName, buf []byte) error {
@@ -229,12 +232,12 @@ func (c *GossipChannel) relayUnicast(dstPeerName PeerName, buf []byte) error {
 	return nil
 }
 
-func (c *GossipChannel) relayBroadcast(srcName PeerName, buf []byte) error {
+func (c *GossipChannel) relayBroadcast(srcName PeerName, update GossipData) error {
 	nextHops := c.ourself.Router.Routes.BroadcastAll(srcName)
 	if len(nextHops) == 0 {
 		return nil
 	}
-	protocolMsg := ProtocolMsg{ProtocolGossipBroadcast, buf}
+	protocolMsg := ProtocolMsg{ProtocolGossipBroadcast, GobEncode(c.hash, srcName, update.Encode())}
 	// FIXME a single blocked connection can stall us
 	for _, conn := range c.ourself.ConnectionsTo(nextHops) {
 		conn.(ProtocolSender).SendProtocolMsg(protocolMsg)
diff --git a/router/router.go b/router/router.go
index 7ef3a9a2..756d39b7 100644
--- a/router/router.go
+++ b/router/router.go
@@ -377,8 +377,8 @@ func (router *Router) OnGossipUnicast(sender PeerName, msg []byte) error {
 	return fmt.Errorf("unexpected topology gossip unicast: %v", msg)
 }
 
-func (router *Router) OnGossipBroadcast(msg []byte) error {
-	return fmt.Errorf("unexpected topology gossip broadcast: %v", msg)
+func (router *Router) OnGossipBroadcast(update []byte) (GossipData, error) {
+	return nil, fmt.Errorf("unexpected topology gossip broadcast: %v", update)
 }
 
 func (router *Router) Gossip() GossipData {