Maintain locale after Symfony2 login

On a multilingual website using Symfony, I have a page with a login form embedded in the sidebar. Let's say I'm on the Spanish version, the current url mysite.com/es

. This page $request->getLocale()

gives me 'es'

everything in order.

However, if I submit a login form to this page, I get to mysite.com

. The part 'es'

in the url has disappeared, but $request->getLocale()

it gives me 'en'

. How can I keep my URL and my locale from changing?

My form:

<form id="login-form" method="POST" action="/login-check">
    <input type="text" id="userEmail" name="_username">
    <input type="password" id="userPassword" name="_password">
    <input type="hidden" name="_csrf_token" value="{{ fos_csrf_provider.generateCsrfToken('authenticate') }}">
</form>

      

        
        
        
      

    

My firewall:

main:
    pattern: ^/
    form_login:
        provider: fos_userbundle
        csrf_provider: form.csrf_provider
        login_path: / 
        check_path: /login_check
    logout:
        path: my_site_logout
        target: /
        success_handler: my_site.logout_success_handler
    anonymous:    true
    remember_me:
        key:        %secret%