Correct way to use Accept header in REST api built with Symfony2 and FOSRestBundle

I am trying to get my webservices to return the correct format when sent with an Accept header. For example, if I submit "Accept: application / xml" it should return in xml format, and if I submit "Accept: application / json" it should return in json format.

This works great if I add the extension. http://example.com/api/users.json returns json and http://example.com/api/users.xml returns XML, But if I don't add extensions it always returns json, completely ignoring the Accept header.

How can I configure it to return whatever is specified in the Accept header if there is no extension?

My config file:

fos_rest:
    format_listener: true
    routing_loader:
        default_format: json
    view:
        view_response_listener: 'force'
        formats:
            json: true
            xml: true
        templating_formats:
            html: true
    serializer:
        serialize_null: true

sensio_framework_extra:
    view:       { annotations: false }
    router:     { annotations: true }

      

        
        
        
      

    

Also tried the following:

format_listener:
    rules:
        - prefer_extension: false

      

        
        
        
      

    

As a result, an error occurred:

Cannot find template "WhateverBundle: Users: getUsers.html.twig"