Fix handling with Firefox
@@ -209,7 +209,7 @@ def _is_websocket(request: web.Request) -> bool:
headers = request.headers
if (
- headers.get(hdrs.CONNECTION, "").lower() == "upgrade"
+ "upgrade" in headers.get(hdrs.CONNECTION, "").lower()
and headers.get(hdrs.UPGRADE, "").lower() == "websocket"
):
return True
