Capybara is sending HTML format on request instead of JS

The feature works perfectly on the browser, however on the tests when Capybara clicks the submit button the request is processed as an HTML:
Processing by SearchController#index as HTML

Instead of:
Processing by SearchController#index as JS

This is my form on the view:
<%= form_with url: search_index_path, local: false, id: 'search-organization', method: :get do |f| %>

I'm using Rspec, capybara and poltergeist.