Problem with "confirmable" gem module "devise" in RubyOnRails

I was implementing the gem Devise in RubyOnRails and everything was working perfectly.

Then I went to add the "confirmable" module. I took the following steps:

I added :confirmable to Usuarios.rb :

class Usuario < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable,
         # adicionado por mim
         :confirmable
end

I created the migration file:

class AddConfirmableToUsuarios < ActiveRecord::Migration
  def change
    change_table(:usuarios) do |t|
      t.string :confirmation_token
      t.datetime :confirmed_at
      t.datetime :confirmation_sent_at
      t.string :unconfirmed_email
    end
  end
end

In the views I had to correct some urls by adding usuario in the helpers, for example:

new_confirmation_path(resource_name)
# para
new_usuario_confirmation_path(resource_name)

But when I submit the form in views/devise/confirmation/new.html.erb I get code 406 "not accptable" and error ActionController::UnknownFormat in Devise::ConfirmationsController#create . Nevertheless, the confirmation email is sent and the link sent is valid and the account can be validated.

Follow the form below:

<h2>Resend confirmation instructions</h2>

<%= form_for(resource, as: resource_name, url: usuario_confirmation_path(resource_name), html: { method: :post }) do |f| %>
  <%= devise_error_messages! %>

  <div><%= f.label :email %><br />
  <%= f.email_field :email, autofocus: true %></div>

  <div><%= f.submit "Resend confirmation instructions" %></div>
<% end %>