class HTTP::Request

def proxy_connect_headers
  connect_headers = HTTP::Headers.coerce(
    Headers::HOST        => headers[Headers::HOST],
    Headers::USER_AGENT  => headers[Headers::USER_AGENT]
  )
  connect_headers[Headers::PROXY_AUTHORIZATION] = proxy_authorization_header if using_authenticated_proxy?
  connect_headers.merge!(proxy[:proxy_headers]) if proxy.key?(:proxy_headers)
  connect_headers
end