diff --git a/src/mux_quic.c b/src/mux_quic.c
index dcf21a726..a8a552cb6 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -3643,8 +3643,10 @@ static void qcc_release(struct qcc *qcc)
 		}
 
 		/* register streams IDs so that quic-conn layer can ignore already closed streams. */
-		qc->rx.stream_max_uni = qcc->largest_uni_r;
-		qc->rx.stream_max_bidi = qcc->largest_bidi_r;
+		if (!conn_is_back(conn)) {
+			qc->rx.stream_max_uni = qcc->largest_uni_r;
+			qc->rx.stream_max_bidi = qcc->largest_bidi_r;
+		}
 	}
 
 	tasklet_free(qcc->wait_event.tasklet);
@@ -3667,7 +3669,7 @@ static void qcc_release(struct qcc *qcc)
 	if (qcc->app_ops) {
 		if (qcc->app_ops->release)
 			qcc->app_ops->release(qcc->ctx);
-		if (conn && conn_is_quic(conn) && conn->handle.qc)
+		if (conn && !conn_is_back(conn) && conn_is_quic(conn) && conn->handle.qc)
 			conn->handle.qc->strm_reject = qcc->app_ops->strm_reject;
 	}
 	TRACE_PROTO("application layer released", QMUX_EV_QCC_END, conn);
diff --git a/src/quic_rx.c b/src/quic_rx.c
index 06b3f3e99..932058f0c 100644
--- a/src/quic_rx.c
+++ b/src/quic_rx.c
@@ -975,11 +975,21 @@ static int qc_parse_pkt_frms(struct quic_conn *qc, struct quic_rx_packet *pkt,
 		{
 			struct qf_stream *strm_frm = &frm->stream;
 			const char fin = frm->type & QUIC_STREAM_FRAME_TYPE_FIN_BIT;
-			const uint64_t max = quic_stream_is_uni(strm_frm->id) ?
-			  qc->rx.stream_max_uni : qc->rx.stream_max_bidi;
+			uint64_t max;
 
 			/* The upper layer may not be allocated. */
 			if (!qc_is_conn_ready(qc)) {
+				if (qc_is_back(qc)) {
+					/* Drain STREAM frames on the backend side. MUX should
+					 * have emitted STOP_SENDING on shut for incomplete streams,
+					 * so the peer should soon stop emission.
+					 */
+					TRACE_DATA("Ignore stream on backend", QUIC_EV_CONN_PRSHPKT, qc);
+					break;
+				}
+
+				max = quic_stream_is_uni(strm_frm->id) ?
+				  qc->rx.stream_max_uni : qc->rx.stream_max_bidi;
 				if (strm_frm->id < max) {
 					TRACE_DATA("Already closed stream", QUIC_EV_CONN_PRSHPKT, qc);
 				}