Symfony 2.8注销不起作用

Question

我是symfony的新手并使用symfony 2.8。我已经开发了一个登录应用程序，它已成功登录，但是当我注销它时显示此错误

InvalidConfigurationException in SecurityExtension.php line 433: 
No authentication listener registered for firewall "secured_area".

我遵循此Link进行注销实施。

Security.yml

security:

encoders:
    AppBundle\Entity\User: bcrypt
# https://symfony.com/doc/current/security.html#b-configuring-how-users-are-loaded
providers:
    our_db_provider:
        entity:
            class: AppBundle:User
            property: email

firewalls:
    # disables authentication for assets and the profiler, adapt it according to your needs
    dev:
        pattern: ^/(_(profiler|wdt)|css|images|js)/
        security: false

    main:
        anonymous: ~
        form_login:
            login_path: login
            check_path: login
        pattern:    ^/
        http_basic: ~
        provider: our_db_provider
        # activate different ways to authenticate

        # https://symfony.com/doc/current/security.html#a-configuring-how-your-users-will-authenticate
        #http_basic: ~

        # https://symfony.com/doc/current/security/form_login_setup.html
        #form_login: ~
    secured_area:
        logout:
            path: /logout
            target: /

的routing.yml

app:
resource: '@AppBundle/Controller/'
type: annotation
logout:
    path: /logout

为什么当我在浏览器中点击/注销时显示此错误，非常感谢任何帮助。