diff --git a/src/mux_quic.c b/src/mux_quic.c
index 8ce0ac71a..21f082770 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -4054,9 +4054,6 @@ static size_t qmux_strm_snd_buf(struct stconn *sc, struct buffer *buf,
 
 	TRACE_ENTER(QMUX_EV_STRM_SEND, qcs->qcc->conn, qcs);
 
-	/* Stream must not be woken up if already waiting for conn buffer. */
-	BUG_ON(LIST_INLIST(&qcs->el_buf));
-
 	/* Sending forbidden if QCS is locally closed (FIN or RESET_STREAM sent). */
 	BUG_ON(qcs_is_close_local(qcs) || (qcs->flags & QC_SF_TO_RESET));
 
@@ -4070,6 +4067,11 @@ static size_t qmux_strm_snd_buf(struct stconn *sc, struct buffer *buf,
 		goto end;
 	}
 
+	if (LIST_INLIST(&qcs->el_buf)) {
+		TRACE_DEVEL("leaving on no buf avail", QMUX_EV_STRM_SEND, qcs->qcc->conn, qcs);
+		goto end;
+	}
+
 	if (qfctl_sblocked(&qcs->qcc->tx.fc)) {
 		TRACE_DEVEL("leaving on connection flow control",
 		            QMUX_EV_STRM_SEND, qcs->qcc->conn, qcs);
@@ -4120,9 +4122,6 @@ static size_t qmux_strm_nego_ff(struct stconn *sc, struct buffer *input,
 
 	TRACE_ENTER(QMUX_EV_STRM_SEND, qcs->qcc->conn, qcs);
 
-	/* Stream must not be woken up if already waiting for conn buffer. */
-	BUG_ON(LIST_INLIST(&qcs->el_buf));
-
 	/* Sending forbidden if QCS is locally closed (FIN or RESET_STREAM sent). */
 	BUG_ON(qcs_is_close_local(qcs) || (qcs->flags & QC_SF_TO_RESET));
 
@@ -4144,6 +4143,12 @@ static size_t qmux_strm_nego_ff(struct stconn *sc, struct buffer *input,
 		goto end;
 	}
 
+	if (LIST_INLIST(&qcs->el_buf)) {
+		TRACE_DEVEL("leaving on no buf avail", QMUX_EV_STRM_SEND, qcs->qcc->conn, qcs);
+		qcs->sd->iobuf.flags |= IOBUF_FL_FF_BLOCKED;
+		goto end;
+	}
+
 	if (qfctl_sblocked(&qcs->qcc->tx.fc)) {
 		TRACE_DEVEL("leaving on connection flow control", QMUX_EV_STRM_SEND, qcs->qcc->conn, qcs);
 		if (!LIST_INLIST(&qcs->el_fctl)) {