diff --git a/src/h3.c b/src/h3.c
index 60b8673c1..9c6b17ea1 100644
--- a/src/h3.c
+++ b/src/h3.c
@@ -1488,6 +1488,8 @@ static int h3_control_send(struct qcs *qcs, void *ctx)
 
 static int h3_resp_headers_send(struct qcs *qcs, struct htx *htx)
 {
+	struct h3s *h3s = qcs->ctx;
+	struct h3c *h3c = h3s->h3c;
 	struct buffer outbuf;
 	struct buffer headers_buf = BUF_NULL;
 	struct buffer *res;
@@ -1521,8 +1523,11 @@ static int h3_resp_headers_send(struct qcs *qcs, struct htx *htx)
 			status = sl->info.res.status;
 		}
 		else if (type == HTX_BLK_HDR) {
-			if (unlikely(hdr >= sizeof(list) / sizeof(list[0]) - 1))
+			if (unlikely(hdr >= sizeof(list) / sizeof(list[0]) - 1)) {
+				TRACE_ERROR("too many headers", H3_EV_TX_FRAME|H3_EV_TX_HDR, qcs->qcc->conn, qcs);
+				h3c->err = H3_INTERNAL_ERROR;
 				goto err;
+			}
 			list[hdr].n = htx_get_blk_name(htx, blk);
 			list[hdr].v = htx_get_blk_value(htx, blk);
 			hdr++;
@@ -1627,6 +1632,8 @@ static int h3_resp_headers_send(struct qcs *qcs, struct htx *htx)
  */
 static int h3_resp_trailers_send(struct qcs *qcs, struct htx *htx)
 {
+	struct h3s *h3s = qcs->ctx;
+	struct h3c *h3c = h3s->h3c;
 	struct buffer headers_buf = BUF_NULL;
 	struct buffer *res;
 	struct http_hdr list[global.tune.max_http_hdr];
@@ -1649,14 +1656,18 @@ static int h3_resp_trailers_send(struct qcs *qcs, struct htx *htx)
 			break;
 
 		if (type == HTX_BLK_TLR) {
-			if (unlikely(hdr >= sizeof(list) / sizeof(list[0]) - 1))
+			if (unlikely(hdr >= sizeof(list) / sizeof(list[0]) - 1)) {
+				TRACE_ERROR("too many headers", H3_EV_TX_FRAME|H3_EV_TX_HDR, qcs->qcc->conn, qcs);
+				h3c->err = H3_INTERNAL_ERROR;
 				goto err;
+			}
 			list[hdr].n = htx_get_blk_name(htx, blk);
 			list[hdr].v = htx_get_blk_value(htx, blk);
 			hdr++;
 		}
 		else {
 			TRACE_ERROR("unexpected HTX block", H3_EV_TX_FRAME|H3_EV_TX_HDR, qcs->qcc->conn, qcs);
+			h3c->err = H3_INTERNAL_ERROR;
 			goto err;
 		}
 	}