CakePHP Containable error: a two level association doesn't work

I do the next query:

        $this->find('all',array(
            'contain' => array(
                'User' => array('id','facebook_id','name','username','Author' => array('first_name','last_name','code','photo')),
                'Tab.code'
            ),
            'fields' => array('Comment.date','Comment.time','Comment.content'),
            'conditions' => array(
                'Tab.code' => $code
            ),
            'limit' => $limit,
            'offset' => $offset
        ));

Comment...

    public $belongsTo = array(
        'User' => array('foreignKey' => 'user_id'),
        'Tab' => array('foreignKey' => 'tab_id')
    );

User...

    public $hasOne = array('Author' => array('foreignKey' => 'id'));

and Author...

    public $belongsTo = array(
        'User' => array(
            'className' => 'User',
            'foreignKey' => 'id'
        )
    );

This returns something like this (in json)...

[
    {
        "Comment": {
            "date": "2001-12-15",
            "time": "17:32:12",
            "content": "..."
        },
        "User": {
            "id": "29",
            "facebook_id": "1234",
            "name": "User 29",
            "username": "user29"
        },
        "Tab": {
            "code": "llibre-de-prova-29",
            "id": "229"
        }
    }
    ...
]

...while I expect that attached to User appears an Author with the fields I specified. Do you know why Author doesn't appear? I did other contains with two levels of recursivity on the code and all works as expected.

Thank you for your help and attention!

Make sure that your model has the Containable behavior attached. It should include the following line:

$actsAs = array('Containable');

Pay attention to make sure that you didn't omit an "s" in "acts" which is a common typo that is hard to spot. You can also attach the Containable behavior on the fly like this:

$this->YourModel->Behaviors->attach('Containable');
$this->YourModel->find('all', array('contain' => array(...)));

Also make sure you type "contain" as the array key, not "contains".