diff --git a/src/mux_quic.c b/src/mux_quic.c
index 78baccb82..9df32be52 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -1158,6 +1158,7 @@ int qcc_realign_stream_txbuf(const struct qcs *qcs, struct buffer *out)
  */
 int qcc_release_stream_txbuf(struct qcs *qcs)
 {
+	struct buffer *buf = qc_stream_buf_get(qcs->stream);
 	const uint64_t bytes = qcs_prep_bytes(qcs);
 
 	/* Cannot release buffer if prepared data is not fully sent. */
@@ -1166,7 +1167,10 @@ int qcc_release_stream_txbuf(struct qcs *qcs)
 		return 1;
 	}
 
+	/* Free released buf size from buf window. */
 	qc_stream_buf_release(qcs->stream);
+	qcc_notify_buf(qcs->qcc, b_size(buf));
+
 	return 0;
 }
 
@@ -1975,7 +1979,7 @@ void qcc_streams_sent_done(struct qcs *qcs, uint64_t data, uint64_t offset)
 		/* Release buffer if everything sent and buf is full or stream is waiting for room. */
 		if (!qcs_prep_bytes(qcs) &&
 		    (b_full(&qcs->stream->buf->buf) || qcs->flags & QC_SF_BLK_MROOM)) {
-			qc_stream_buf_release(qcs->stream);
+			qcc_release_stream_txbuf(qcs);
 			qcs->flags &= ~QC_SF_BLK_MROOM;
 			qcs_notify_send(qcs);
 		}
diff --git a/src/quic_stream.c b/src/quic_stream.c
index bf9a54e62..587b5a1ca 100644
--- a/src/quic_stream.c
+++ b/src/quic_stream.c
@@ -30,15 +30,22 @@ static void qc_stream_buf_free(struct qc_stream_desc *stream,
 {
 	struct quic_conn *qc = stream->qc;
 	struct buffer *buf = &(*stream_buf)->buf;
-	uint64_t free_size;
 
 	LIST_DEL_INIT(&(*stream_buf)->list);
 
 	/* Reset current buf ptr if deleted instance is the same one. */
-	if (*stream_buf == stream->buf)
+	if (*stream_buf == stream->buf) {
 		stream->buf = NULL;
 
-	free_size = b_size(buf);
+		/* Only non-released buffer are notified to MUX layer. */
+		if (qc->mux_state == QC_MUX_READY) {
+			if (!(stream->flags & QC_SD_FL_OOB_BUF)) {
+				/* notify MUX about available buffers. */
+				qcc_notify_buf(qc->qcc, b_size(buf));
+			}
+		}
+	}
+
 	if ((*stream_buf)->sbuf) {
 		pool_free(pool_head_sbuf, buf->area);
 	}
@@ -48,14 +55,6 @@ static void qc_stream_buf_free(struct qc_stream_desc *stream,
 	}
 	pool_free(pool_head_quic_stream_buf, *stream_buf);
 	*stream_buf = NULL;
-
-	/* notify MUX about available buffers. */
-	if (qc->mux_state == QC_MUX_READY) {
-		if (!(stream->flags & QC_SD_FL_OOB_BUF)) {
-			/* notify MUX about available buffers. */
-			qcc_notify_buf(qc->qcc, free_size);
-		}
-	}
 }
 
 /* Allocate a new stream descriptor with id <id>. The caller is responsible to
@@ -124,6 +123,9 @@ void qc_stream_desc_release(struct qc_stream_desc *stream,
 		/* final_size cannot be greater than all currently stored data. */
 		BUG_ON(final_size > tail_offset);
 
+		/* release buffer and notify MUX. */
+		qcc_notify_buf(stream->qc->qcc, b_size(buf));
+
 		/* Remove unsent data from current buffer. */
 		if (final_size < tail_offset)
 			b_sub(buf, tail_offset - final_size);
@@ -209,7 +211,6 @@ void qc_stream_desc_free(struct qc_stream_desc *stream, int closing)
 	struct quic_conn *qc = stream->qc;
 	struct eb64_node *frm_node;
 	unsigned int free_count = 0;
-	uint64_t free_size = 0;
 
 	/* This function only deals with released streams. */
 	BUG_ON(!(stream->flags & QC_SD_FL_RELEASE));
@@ -217,7 +218,6 @@ void qc_stream_desc_free(struct qc_stream_desc *stream, int closing)
 	/* free remaining stream buffers */
 	list_for_each_entry_safe(buf, buf_back, &stream->buf_list, list) {
 		if (!(b_data(&buf->buf)) || closing) {
-			free_size += b_size(&buf->buf);
 			if (buf->sbuf)
 				pool_free(pool_head_sbuf, buf->buf.area);
 			else
@@ -228,17 +228,9 @@ void qc_stream_desc_free(struct qc_stream_desc *stream, int closing)
 		}
 	}
 
-	if (free_count) {
+	if (free_count)
 		offer_buffers(NULL, free_count);
 
-		if (qc->mux_state == QC_MUX_READY) {
-			if (!(stream->flags & QC_SD_FL_OOB_BUF)) {
-				/* notify MUX about available buffers. */
-				qcc_notify_buf(qc->qcc, free_size);
-			}
-		}
-	}
-
 	/* qc_stream_desc might be freed before having received all its ACKs.
 	 * This is the case if some frames were retransmitted.
 	 */