diff --git a/router/local_peer.go b/router/local_peer.go
index 9d0356f2..1b1160f5 100644
--- a/router/local_peer.go
+++ b/router/local_peer.go
@@ -250,7 +250,7 @@ func (peer *LocalPeer) handleConnectionEstablished(conn *LocalConnection) {
 
 func (peer *LocalPeer) handleSendProtocolMsg(m ProtocolMsg) {
 	peer.ForEachConnection(func(_ PeerName, conn Connection) {
-		conn.(*LocalConnection).SendProtocolMsg(m)
+		conn.(ProtocolSender).SendProtocolMsg(m)
 	})
 }
 
diff --git a/router/protocol.go b/router/protocol.go
index 1d8cd104..2218d813 100644
--- a/router/protocol.go
+++ b/router/protocol.go
@@ -21,3 +21,7 @@ type ProtocolMsg struct {
 	tag ProtocolTag
 	msg []byte
 }
+
+type ProtocolSender interface {
+	SendProtocolMsg(m ProtocolMsg)
+}