diff --git a/src/mux_pt.c b/src/mux_pt.c
index beca8c2..4195ec2 100644
--- a/src/mux_pt.c
+++ b/src/mux_pt.c
@@ -116,6 +116,11 @@
 {
 	size_t ret;
 
+	if (!count) {
+		cs->flags |= CS_FL_RCV_MORE;
+		return 0;
+	}
+	cs->flags &= ~CS_FL_RCV_MORE;
 	ret = cs->conn->xprt->rcv_buf(cs->conn, buf, count, flags);
 	if (conn_xprt_read0_pending(cs->conn))
 		cs->flags |= CS_FL_EOS;
diff --git a/src/stream_interface.c b/src/stream_interface.c
index 46fc9eb..65d2c61 100644
--- a/src/stream_interface.c
+++ b/src/stream_interface.c
@@ -1226,13 +1226,11 @@
 	 */
 	while (!(conn->flags & (CO_FL_ERROR | CO_FL_WAIT_ROOM | CO_FL_HANDSHAKE)) &&
 	       !(cs->flags & (CS_FL_ERROR|CS_FL_EOS)) && !(ic->flags & CF_SHUTR)) {
+		/* <max> may be null. This is the mux responsibility to set
+		 * CS_FL_RCV_MORE on the CS if more space is needed.
+		 */
 		max = channel_recv_max(ic);
 
-		if (!max) {
-			si_cant_put(si);
-			break;
-		}
-
 		ret = cs->conn->mux->rcv_buf(cs, &ic->buf, max, co_data(ic) ? CO_RFL_BUF_WET : 0);
 		if (cs->flags & CS_FL_RCV_MORE)
 			si_cant_put(si);