diff --git a/include/haproxy/mux_h1-t.h b/include/haproxy/mux_h1-t.h
index 23b5822186..8d4c3a4add 100644
--- a/include/haproxy/mux_h1-t.h
+++ b/include/haproxy/mux_h1-t.h
@@ -101,6 +101,7 @@ static forceinline char *h1c_show_flags(char *buf, size_t len, const char *delim
 
 #define H1S_F_HAVE_SRV_NAME  0x00002000 /* Set during output process if the server name header was added to the request */
 #define H1S_F_HAVE_O_CONN    0x00004000 /* Set during output process to know connection mode was processed */
+#define H1S_F_HAVE_WS_KEY    0x00008000 /* Set during output process to know WS key was found or generated */
 
 /* This function is used to report flags in debugging tools. Please reflect
  * below any single-bit flag addition above in the same order via the
@@ -116,7 +117,7 @@ static forceinline char *h1s_show_flags(char *buf, size_t len, const char *delim
 	_(H1S_F_WANT_KAL, _(H1S_F_WANT_TUN, _(H1S_F_WANT_CLO,
 	_(H1S_F_NOT_FIRST, _(H1S_F_BODYLESS_RESP,
 	_(H1S_F_INTERNAL_ERROR, _(H1S_F_NOT_IMPL_ERROR, _(H1S_F_PARSING_ERROR, _(H1S_F_PROCESSING_ERROR,
-	_(H1S_F_HAVE_SRV_NAME, _(H1S_F_HAVE_O_CONN))))))))))))));
+	_(H1S_F_HAVE_SRV_NAME, _(H1S_F_HAVE_O_CONN, _(H1S_F_HAVE_WS_KEY)))))))))))))));
 	/* epilogue */
 	_(~0U);
 	return buf;
diff --git a/src/mux_h1.c b/src/mux_h1.c
index d600c78f8c..36a55f9765 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -1938,7 +1938,6 @@ static size_t h1_process_mux(struct h1c *h1c, struct buffer *buf, size_t count)
 	struct buffer tmp;
 	size_t total = 0;
 	int last_data = 0;
-	int ws_key_found = 0;
 
 	chn_htx = htxbuf(buf);
 	TRACE_ENTER(H1_EV_TX_DATA, h1c->conn, h1s, chn_htx, (size_t[]){count});
@@ -2150,7 +2149,7 @@ static size_t h1_process_mux(struct h1c *h1c, struct buffer *buf, size_t count)
 				          h1m->flags & H1_MF_RESP) ||
 				         (isteq(n, ist("sec-websocket-key")) &&
 				          !(h1m->flags & H1_MF_RESP))) {
-					ws_key_found = 1;
+					h1s->flags |= H1S_F_HAVE_WS_KEY;
 				}
 				else if (isteq(n, ist("te"))) {
 					/* "te" may only be sent with "trailers" if this value
@@ -2251,8 +2250,8 @@ static size_t h1_process_mux(struct h1c *h1c, struct buffer *buf, size_t count)
 				}
 
 				/* Add websocket handshake key if needed */
-				if ((h1m->flags & (H1_MF_CONN_UPG|H1_MF_UPG_WEBSOCKET)) == (H1_MF_CONN_UPG|H1_MF_UPG_WEBSOCKET) &&
-				    !ws_key_found) {
+				if (!(h1s->flags & H1S_F_HAVE_WS_KEY) &&
+				    (h1m->flags & (H1_MF_CONN_UPG|H1_MF_UPG_WEBSOCKET)) == (H1_MF_CONN_UPG|H1_MF_UPG_WEBSOCKET)) {
 					if (!(h1m->flags & H1_MF_RESP)) {
 						/* generate a random websocket key
 						 * stored in the session to
@@ -2276,6 +2275,7 @@ static size_t h1_process_mux(struct h1c *h1c, struct buffer *buf, size_t count)
 							goto full;
 						}
 					}
+					h1s->flags |= H1S_F_HAVE_WS_KEY;
 				}
 
 				TRACE_PROTO((!(h1m->flags & H1_MF_RESP) ? "H1 request headers xferred" : "H1 response headers xferred"),