diff --git a/src/h3.c b/src/h3.c
index fac9846d9..68e302dfa 100644
--- a/src/h3.c
+++ b/src/h3.c
@@ -675,6 +675,15 @@ static ssize_t h3_headers_to_htx(struct qcs *qcs, const struct buffer *buf,
 				len = -1;
 				goto out;
 			}
+
+			if (!http_validate_scheme(list[hdr_idx].v)) {
+				TRACE_ERROR("invalid scheme pseudo-header", H3_EV_RX_FRAME|H3_EV_RX_HDR, qcs->qcc->conn, qcs);
+				h3s->err = H3_ERR_MESSAGE_ERROR;
+				qcc_report_glitch(h3c->qcc, 1);
+				len = -1;
+				goto out;
+			}
+
 			scheme = list[hdr_idx].v;
 		}
 		else if (isteq(list[hdr_idx].n, ist(":authority"))) {