diff --git a/src/mux_h1.c b/src/mux_h1.c
index 92eea1867..1e4041bd7 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -1518,6 +1518,8 @@ static size_t h1_process_output(struct h1c *h1c, struct buffer *buf, size_t coun
 				if (!htx_reqline_to_h1(sl, tmp))
 					goto copy;
 				h1m->flags |= H1_MF_XFER_LEN;
+				if (sl->flags & HTX_SL_F_BODYLESS)
+					h1m->flags |= H1_MF_CLEN;
 				h1m->state = H1_MSG_HDR_FIRST;
 				break;
 
@@ -1582,10 +1584,12 @@ static size_t h1_process_output(struct h1c *h1c, struct buffer *buf, size_t coun
 					}
 				}
 
-				if (h1s->status >= 200 && h1s->status != 204 && h1s->status != 304 &&
-				    h1s->meth != HTTP_METH_HEAD && !(h1s->meth == HTTP_METH_CONNECT && h1s->status == 200) &&
-				    (h1m->flags & (H1_MF_VER_11|H1_MF_RESP|H1_MF_CLEN|H1_MF_CHNK|H1_MF_XFER_LEN)) ==
-				    (H1_MF_VER_11|H1_MF_RESP|H1_MF_XFER_LEN)) {
+				if (((h1m->flags & (H1_MF_VER_11|H1_MF_RESP|H1_MF_CLEN|H1_MF_CHNK|H1_MF_XFER_LEN)) ==
+				     (H1_MF_VER_11|H1_MF_XFER_LEN)) ||
+				    (h1s->status >= 200 && h1s->status != 204 && h1s->status != 304 &&
+				     h1s->meth != HTTP_METH_HEAD && !(h1s->meth == HTTP_METH_CONNECT && h1s->status == 200) &&
+				     (h1m->flags & (H1_MF_VER_11|H1_MF_RESP|H1_MF_CLEN|H1_MF_CHNK|H1_MF_XFER_LEN)) ==
+				     (H1_MF_VER_11|H1_MF_RESP|H1_MF_XFER_LEN))) {
 					/* chunking needed but header not seen */
 					if (!chunk_memcat(tmp, "transfer-encoding: chunked\r\n", 28))
 						goto copy;