The security context contains no authentication token ESI and Symfony2

Question

I'm using ESI (Edge Side Includes) to speed up my page but every time that I want to check if the user is loged in or not I get this error:

AuthenticationCredentialsNotFoundException: The security context contains no authentication token. One possible reason may be that there is no firewall configured for this URL.

In my config.yml file I have this:

  **esi:             true<br>
  fragments:       { path: /_proxy }<br>
  trusted_proxies: [127.0.0.1]**

Does someone knows how to solve it? I already tried to set a firewall for the /_proxy urls but I think that this is not the solution.

These are my firewalls:

main:
   pattern:    ^/
   form_login:
      check_path: /user/login_check
      login_path: /user/login
      provider: chain_provider
      failure_path:   null
   logout:
      path:   /user/logout
      target: /
      success_handler: logout_success_handler
      invalidate_session: true
   anonymous: ~
   security: true      
dev:
   pattern:  ^/(_(profiler|wdt)|css|images|js)/
   security: false

Thanks