diff --git a/src/h2.c b/src/h2.c
index 64c23d474..ef30384ce 100644
--- a/src/h2.c
+++ b/src/h2.c
@@ -319,6 +319,7 @@ static struct htx_sl *h2_prepare_htx_reqline(uint32_t fields, struct ist *phdr,
  */
 int h2_make_htx_request(struct http_hdr *list, struct htx *htx, unsigned int *msgf, unsigned long long *body_len, int relaxed)
 {
+	struct htx_blk *tailblk = htx_get_tail_blk(htx);
 	struct ist phdr_val[H2_PHDR_NUM_ENTRIES];
 	uint32_t fields; /* bit mask of H2_PHDR_FND_* */
 	uint32_t idx;
@@ -533,6 +534,7 @@ int h2_make_htx_request(struct http_hdr *list, struct htx *htx, unsigned int *ms
 	return ret;
 
  fail:
+	htx_truncate_blk(htx, tailblk);
 	return -1;
 }
 
@@ -637,6 +639,7 @@ static struct htx_sl *h2_prepare_htx_stsline(uint32_t fields, struct ist *phdr,
  */
 int h2_make_htx_response(struct http_hdr *list, struct htx *htx, unsigned int *msgf, unsigned long long *body_len, char *upgrade_protocol)
 {
+	struct htx_blk *tailblk = htx_get_tail_blk(htx);
 	struct ist phdr_val[H2_PHDR_NUM_ENTRIES];
 	uint32_t fields; /* bit mask of H2_PHDR_FND_* */
 	uint32_t idx;
@@ -793,6 +796,7 @@ int h2_make_htx_response(struct http_hdr *list, struct htx *htx, unsigned int *m
 	return ret;
 
  fail:
+	htx_truncate_blk(htx, tailblk);
 	return -1;
 }
 
@@ -812,6 +816,7 @@ int h2_make_htx_response(struct http_hdr *list, struct htx *htx, unsigned int *m
  */
 int h2_make_htx_trailers(struct http_hdr *list, struct htx *htx)
 {
+	struct htx_blk *tailblk = htx_get_tail_blk(htx);
 	const char *ctl;
 	struct ist v;
 	uint32_t idx;
@@ -871,5 +876,6 @@ int h2_make_htx_trailers(struct http_hdr *list, struct htx *htx)
 	return 1;
 
  fail:
+	htx_truncate_blk(htx, tailblk);
 	return -1;
 }
diff --git a/src/h3.c b/src/h3.c
index 09634f14c..ef6502d77 100644
--- a/src/h3.c
+++ b/src/h3.c
@@ -1111,6 +1111,7 @@ static ssize_t h3_resp_headers_to_htx(struct qcs *qcs, const struct buffer *buf,
 	struct buffer *tmp = get_trash_chunk();
 	struct htx *htx = NULL;
 	struct htx_sl *sl;
+	struct htx_blk *tailblk = NULL;
 	struct http_hdr list[global.tune.max_http_hdr * 2];
 	unsigned int flags = HTX_SL_F_NONE;
 	struct ist status = IST_NULL;
@@ -1161,7 +1162,7 @@ static ssize_t h3_resp_headers_to_htx(struct qcs *qcs, const struct buffer *buf,
 	}
 	BUG_ON(!b_size(appbuf)); /* TODO */
 	htx = htx_from_buf(appbuf);
-
+	tailblk = htx_get_tail_blk(htx);
 	/* Only handle one HEADERS frame at a time. Thus if HTX buffer is too
 	 * small, it happens solely from a single frame and the only option is
 	 * to close the stream.
@@ -1351,8 +1352,11 @@ static ssize_t h3_resp_headers_to_htx(struct qcs *qcs, const struct buffer *buf,
 	}
 
  out:
-	if (appbuf)
+	if (appbuf) {
+		if ((ssize_t)len < 0)
+			htx_truncate_blk(htx, tailblk);
 		htx_to_buf(htx, appbuf);
+	}
 
 	TRACE_LEAVE(H3_EV_RX_FRAME|H3_EV_RX_HDR, qcs->qcc->conn, qcs);
 	return len;
@@ -1376,6 +1380,7 @@ static ssize_t h3_trailers_to_htx(struct qcs *qcs, const struct buffer *buf,
 	struct buffer *appbuf = NULL;
 	struct htx *htx = NULL;
 	struct htx_sl *sl;
+	struct htx_blk *tailblk = NULL;
 	struct http_hdr list[global.tune.max_http_hdr * 2];
 	int hdr_idx, ret;
 	const char *ctl;
@@ -1406,6 +1411,7 @@ static ssize_t h3_trailers_to_htx(struct qcs *qcs, const struct buffer *buf,
 	}
 	BUG_ON(!b_size(appbuf)); /* TODO */
 	htx = htx_from_buf(appbuf);
+	tailblk = htx_get_tail_blk(htx);
 
 	if (!h3s->data_len) {
 		/* Notify that no body is present. This can only happens if
@@ -1521,8 +1527,11 @@ static ssize_t h3_trailers_to_htx(struct qcs *qcs, const struct buffer *buf,
 
  out:
 	/* HTX may be non NULL if error before previous htx_to_buf(). */
-	if (appbuf)
+	if (appbuf) {
+		if ((ssize_t)len < 0)
+			htx_truncate_blk(htx, tailblk);
 		htx_to_buf(htx, appbuf);
+	}
 
 	TRACE_LEAVE(H3_EV_RX_FRAME|H3_EV_RX_HDR, qcs->qcc->conn, qcs);
 	return len;