diff --git a/include/haproxy/h1.h b/include/haproxy/h1.h
index a9d01d047..25d3e5fd0 100644
--- a/include/haproxy/h1.h
+++ b/include/haproxy/h1.h
@@ -98,7 +98,7 @@ enum h1m_state {
 #define H1_MF_UPG_WEBSOCKET     0x00008000 // Set for a Websocket upgrade handshake
 #define H1_MF_TE_CHUNKED        0x00010000 // T-E "chunked"
 #define H1_MF_TE_OTHER          0x00020000 // T-E other than supported ones found (only "chunked" is supported for now)
-#define H1_MF_UPG_H2C           0x00040000 // "h2c" or "h2" used as upgrade token
+/* unused: 0x00040000 */
 #define H1_MF_NOT_HTTP           0x00080000 // Not an HTTP message (e.g "RTSP", only possible if invalid message are accepted)
 /* Mask to use to reset H1M flags when we restart headers parsing.
  *
@@ -160,7 +160,7 @@ int h1_headers_to_hdr_list(char *start, const char *stop,
 
 int h1_parse_xfer_enc_header(struct h1m *h1m, struct ist value);
 void h1_parse_connection_header(struct h1m *h1m, struct ist *value);
-void h1_parse_upgrade_header(struct h1m *h1m, struct ist value);
+void h1_parse_upgrade_header(struct h1m *h1m, struct ist *value);
 
 void h1_generate_random_ws_input_key(char key_out[25]);
 void h1_calculate_ws_output_key(const char *key, char *result);
diff --git a/src/h1.c b/src/h1.c
index 7fb78804f..792737c9e 100644
--- a/src/h1.c
+++ b/src/h1.c
@@ -274,17 +274,19 @@ void h1_parse_connection_header(struct h1m *h1m, struct ist *value)
 
 /* Parse the Upgrade: header of an HTTP/1 request.
  * If "websocket" is found, set H1_MF_UPG_WEBSOCKET flag
- * If "h2c" or "h2" found, set H1_MF_UPG_H2C flag.
+ * If "h2c" or "h2" found, the value is skipped.
  */
-void h1_parse_upgrade_header(struct h1m *h1m, struct ist value)
+void h1_parse_upgrade_header(struct h1m *h1m, struct ist *value)
 {
-	char *e, *n;
+	char *e, *n, *p;
 	struct ist word;
 
-	h1m->flags &= ~(H1_MF_UPG_WEBSOCKET|H1_MF_UPG_H2C);
+	h1m->flags &= ~H1_MF_UPG_WEBSOCKET;
 
-	word.ptr = value.ptr - 1; // -1 for next loop's pre-increment
-	e = istend(value);
+	word.ptr = value->ptr - 1; // -1 for next loop's pre-increment
+	p = value->ptr;
+	e = value->ptr + value->len;
+	value->len = 0;
 
 	while (++word.ptr < e) {
 		/* skip leading delimiter and blanks */
@@ -301,9 +303,20 @@ void h1_parse_upgrade_header(struct h1m *h1m, struct ist value)
 		if (isteqi(word, ist("websocket")))
 			h1m->flags |= H1_MF_UPG_WEBSOCKET;
 		else if (isteqi(word, ist("h2c")) || isteqi(word, ist("h2")))
-			h1m->flags |= H1_MF_UPG_H2C;
+			goto skip_val;
 
-		word.ptr = n;
+		if (value->ptr + value->len == p) {
+			/* no rewrite done till now */
+			value->len = n - value->ptr;
+		}
+		else {
+			if (value->len)
+				value->ptr[value->len++] = ',';
+			istcat(value, word, e - value->ptr);
+		}
+
+	  skip_val:
+		word.ptr = p = n;
 	}
 }
 
@@ -983,7 +996,11 @@ int h1_headers_to_hdr_list(char *start, const char *stop,
 					}
 				}
 				else if (isteqi(n, ist("upgrade"))) {
-					h1_parse_upgrade_header(h1m, v);
+					h1_parse_upgrade_header(h1m, &v);
+					if (!v.len) {
+						/* skip it */
+						break;
+					}
 				}
 				else if (!(h1m->flags & H1_MF_RESP) && isteqi(n, ist("host"))) {
 					if (host_idx == -1) {
diff --git a/src/h1_htx.c b/src/h1_htx.c
index 9e2996e19..d0837abbc 100644
--- a/src/h1_htx.c
+++ b/src/h1_htx.c
@@ -215,20 +215,6 @@ static int h1_postparse_req_hdrs(struct h1m *h1m, union h1_sl *h1sl, struct htx
 
 	flags |= h1m_htx_sl_flags(h1m);
 
-	/* Remove Upgrade header in problematic cases :
-	 * - "h2c" or "h2" token specified as token
-	 */
-	if ((h1m->flags & (H1_MF_CONN_UPG|H1_MF_UPG_H2C)) == (H1_MF_CONN_UPG|H1_MF_UPG_H2C)) {
-		int i;
-
-		for (i = 0; hdrs[i].n.len; i++) {
-			if (isteqi(hdrs[i].n, ist("upgrade")))
-				hdrs[i].v = IST_NULL;
-		}
-		h1m->flags &=~ H1_MF_CONN_UPG;
-		flags &= ~HTX_SL_F_CONN_UPG;
-	}
-
 	sl = htx_add_stline(htx, HTX_BLK_REQ_SL, flags, meth, uri, vsn);
 	if (!sl || !htx_add_all_headers(htx, hdrs))
 		goto error;
diff --git a/src/mux_h1.c b/src/mux_h1.c
index 982d267b7..cb95556c7 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -2713,7 +2713,9 @@ static size_t h1_make_headers(struct h1s *h1s, struct h1m *h1m, struct htx *htx,
 					goto nextblk;
 			}
 			else if (isteq(n, ist("upgrade"))) {
-				h1_parse_upgrade_header(h1m, v);
+				h1_parse_upgrade_header(h1m, &v);
+				if (!v.len)
+					goto nextblk;
 			}
 			else if ((isteq(n, ist("sec-websocket-accept")) && h1m->flags & H1_MF_RESP) ||
 				 (isteq(n, ist("sec-websocket-key")) && !(h1m->flags & H1_MF_RESP))) {