Capybara not working with action_cable

I'm using the Rails 5 beta 3 with action cable, the integration works fine in development but when I try to run a feature test through capybara, it doesn't seem to hit the channel actions.

I'm using Portergeist and configured puma as capybara's server. Also I'm using es5-shim and es6-shim.

Has anyone else experienced this or knows any workaround?

Thanks!

Edit

Im using this capybara branch to configure Puma in Capybara

Capybara.register_server :puma do |app, port, host|
  require 'puma'
  Puma::Server.new(app).tap do |s|
    s.add_tcp_listener host, port
  end.run.join
end

I have not set anything on config.action_cable.allowed_request_origins