diff --git a/include/proto/connection.h b/include/proto/connection.h
index c677fb29a..e4621ccbd 100644
--- a/include/proto/connection.h
+++ b/include/proto/connection.h
@@ -44,9 +44,6 @@ int init_connection();
  */
 void conn_fd_handler(int fd);
 
-/* conn_stream functions */
-size_t __cs_send(struct conn_stream *cs, struct buffer *buf, size_t count, int flags);
-
 /* receive a PROXY protocol header over a connection */
 int conn_recv_proxy(struct connection *conn, int flag);
 int make_proxy_line(char *buf, int buf_len, struct server *srv, struct connection *remote);
@@ -303,17 +300,6 @@ static inline void cs_update_mux_polling(struct conn_stream *cs)
 		conn->mux->update_poll(cs);
 }
 
-/* conn_stream send function. Uses mux->snd_buf() if defined, otherwise
- * falls back to __cs_send().
- */
-static inline size_t cs_send(struct conn_stream *cs, struct buffer *buf, size_t count, int flags)
-{
-	if (cs->conn->mux->snd_buf)
-		return cs->conn->mux->snd_buf(cs, buf, count, flags);
-	else
-		return __cs_send(cs, buf, count, flags);
-}
-
 /***** Event manipulation primitives for use by DATA I/O callbacks *****/
 /* The __conn_* versions do not propagate to lower layers and are only meant
  * to be used by handlers called by the connection handler. The other ones
@@ -615,7 +601,6 @@ static inline void cs_init(struct conn_stream *cs, struct connection *conn)
 	LIST_INIT(&cs->wait_list.list);
 	LIST_INIT(&cs->send_wait_list);
 	cs->conn = conn;
-	cs->txbuf = BUF_NULL;
 }
 
 /* Initializes all required fields for a new connection. Note that it does the
@@ -676,17 +661,6 @@ static inline struct connection *conn_new()
 	return conn;
 }
 
-/* Releases the conn_stream's tx buf if it exists. The buffer is automatically
- * replaced with a pointer to the empty buffer.
- */
-static inline void cs_drop_txbuf(struct conn_stream *cs)
-{
-	if (b_size(&cs->txbuf)) {
-		b_free(&cs->txbuf);
-		offer_buffers(NULL, tasks_run_queue);
-	}
-}
-
 /* Releases a conn_stream previously allocated by cs_new(), as well as any
  * buffer it would still hold.
  */
@@ -695,7 +669,6 @@ static inline void cs_free(struct conn_stream *cs)
 	if (cs->wait_list.task)
 		tasklet_free(cs->wait_list.task);
 
-	cs_drop_txbuf(cs);
 	pool_free(pool_head_connstream, cs);
 }
 
diff --git a/include/types/connection.h b/include/types/connection.h
index f16b0cd94..abe85a477 100644
--- a/include/types/connection.h
+++ b/include/types/connection.h
@@ -372,7 +372,6 @@ struct conn_stream {
 	struct connection *conn;             /* xprt-level connection */
 	struct wait_list wait_list;          /* We're in a wait list for send */
 	struct list send_wait_list;          /* list of tasks to wake when we're ready to send */
-	struct buffer txbuf;                 /* transmission buffer, always valid (buf_empty or real buffer) */
 	void *data;                          /* pointer to upper layer's entity (eg: stream interface) */
 	const struct data_cb *data_cb;       /* data layer callbacks. Must be set before xprt->init() */
 	void *ctx;                           /* mux-specific context */
diff --git a/src/checks.c b/src/checks.c
index bb50548a1..fa04bc805 100644
--- a/src/checks.c
+++ b/src/checks.c
@@ -771,7 +771,7 @@ static void __event_srv_chk_w(struct conn_stream *cs)
 		goto out;
 
 	if (b_data(&check->bo)) {
-		cs_send(cs, &check->bo, b_data(&check->bo), 0);
+		cs->conn->mux->snd_buf(cs, &check->bo, b_data(&check->bo), 0);
 		b_realign_if_empty(&check->bo);
 		if (conn->flags & CO_FL_ERROR || cs->flags & CS_FL_ERROR) {
 			chk_report_conn_err(check, errno, 0);
@@ -2699,7 +2699,7 @@ static int tcpcheck_main(struct check *check)
 			int ret;
 
 			__cs_want_send(cs);
-			ret = cs_send(cs, &check->bo, b_data(&check->bo), 0);
+			ret = cs->conn->mux->snd_buf(cs, &check->bo, b_data(&check->bo), 0);
 			b_realign_if_empty(&check->bo);
 
 			if (ret <= 0) {
diff --git a/src/connection.c b/src/connection.c
index 2a7fb1b47..df3df8426 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -383,17 +383,6 @@ int conn_sock_drain(struct connection *conn)
 	return 1;
 }
 
-/*
- * default cs send() : this one is used when mux->snd_buf == NULL. It puts up to
- * <count> bytes from <buf> into cs->txbuf. The number of bytes transferred is
- * returned. Here we don't care if cs->txbuf is allocated or not. If not, it
- * will be swapped with <buf>.
- */
-size_t __cs_send(struct conn_stream *cs, struct buffer *buf, size_t count, int flags)
-{
-	return b_xfer(&cs->txbuf, buf, count);
-}
-
 /*
  * Get data length from tlv
  */
diff --git a/src/stream_interface.c b/src/stream_interface.c
index 591d8352b..f2d6b6f5b 100644
--- a/src/stream_interface.c
+++ b/src/stream_interface.c
@@ -721,7 +721,7 @@ static struct task * si_cs_send(struct task *t, void *ctx, unsigned short state)
 		if (oc->flags & CF_STREAMER)
 			send_flag |= CO_SFL_STREAMER;
 
-		ret = cs_send(cs, &oc->buf, co_data(oc), send_flag);
+		ret = cs->conn->mux->snd_buf(cs, &oc->buf, co_data(oc), send_flag);
 		if (ret > 0) {
 			did_send = 1;
 			oc->flags |= CF_WRITE_PARTIAL | CF_WROTE_DATA | CF_WRITE_EVENT;