diff --git a/core.c b/core.c
index c11564a..71b54ce 100644
--- a/core.c
+++ b/core.c
@@ -238,13 +238,14 @@
 	mctp->busses[0].binding = binding;
 	mctp->busses[0].eid = eid;
 	binding->bus = &mctp->busses[0];
+	binding->mctp = mctp;
 	return 0;
 }
 
-void mctp_bus_rx(struct mctp *mctp, struct mctp_binding *binding,
-		struct mctp_pktbuf *pkt)
+void mctp_bus_rx(struct mctp_binding *binding, struct mctp_pktbuf *pkt)
 {
 	struct mctp_bus *bus = binding->bus;
+	struct mctp *mctp = binding->mctp;
 	struct mctp_msg_ctx *ctx;
 	struct mctp_hdr *hdr;
 	uint8_t flags, seq, tag;
@@ -318,8 +319,7 @@
 	}
 }
 
-static int mctp_packet_tx(struct mctp *mctp __attribute__((unused)),
-		struct mctp_bus *bus,
+static int mctp_packet_tx(struct mctp_bus *bus,
 		struct mctp_pktbuf *pkt)
 {
 	return bus->binding->tx(bus->binding, pkt);
@@ -370,7 +370,7 @@
 	for (pkt = mctp->tx_queue_head; pkt;) {
 		mctp_prdebug("sending pkt, len %d",
 				mctp_pktbuf_size(pkt));
-		mctp_packet_tx(mctp, bus, pkt);
+		mctp_packet_tx(bus, pkt);
 		tmp = pkt->next;
 		mctp_pktbuf_free(pkt);
 		pkt = tmp;
diff --git a/libmctp.h b/libmctp.h
index c477a2a..291b639 100644
--- a/libmctp.h
+++ b/libmctp.h
@@ -82,12 +82,12 @@
 	const char	*name;
 	uint8_t		version;
 	struct mctp_bus	*bus;
+	struct mctp	*mctp;
 	int		(*tx)(struct mctp_binding *binding,
 				struct mctp_pktbuf *pkt);
 };
 
-void mctp_bus_rx(struct mctp *mctp, struct mctp_binding *binding,
-		struct mctp_pktbuf *pkt);
+void mctp_bus_rx(struct mctp_binding *binding, struct mctp_pktbuf *pkt);
 
 /* environment-specific allocation */
 void mctp_set_alloc_ops(void *(*alloc)(size_t),
diff --git a/serial.c b/serial.c
index 482cedb..c9f6c90 100644
--- a/serial.c
+++ b/serial.c
@@ -19,7 +19,6 @@
 
 struct mctp_binding_serial {
 	struct mctp_binding	binding;
-	struct mctp		*mctp;
 	int			fd;
 	unsigned long		bus_id;
 
@@ -138,7 +137,7 @@
 	assert(pkt);
 
 	if (valid)
-		mctp_bus_rx(serial->mctp, &serial->binding, pkt);
+		mctp_bus_rx(&serial->binding, pkt);
 
 	mctp_pktbuf_free(pkt);
 	serial->rx_pkt = NULL;
@@ -294,7 +293,6 @@
 		struct mctp *mctp, mctp_eid_t eid)
 {
 	assert(serial->fd >= 0);
-	serial->mctp = mctp;
 	mctp_register_bus(mctp, &serial->binding, eid);
 }