Associations between 2 tables with Doctrine 2 not found

I'm trying to workout a basic join in a query for MySQL-tables. After reading the documentation and some questions on Stackoverflow, I still can't get it to work ...

The error: Message: [Semantical Error] line 0, col 74 near 'o': Error: Class Client_Model_Client has no association named Contact_Model_Contact

The code here, are my models and the query I'm working on:

Model client

<?php
/**
 * @Table(name="client_clients")
 * @Entity(repositoryClass="Client_Model_ClientRepository")
 */
class Client_Model_Client {

public function __construct()
{
    $this->contacts = new \Doctrine\Common\开发者_StackOverflowCollections\ArrayCollection();
}

/**
 * @var integer $id
 * @Id @Column(type="integer") 
 * @GeneratedValue
 */
private $id;

/**
 * @var string $name
 * @Column(type="string")
 */
private $name;

/**
 * @var string $address
 * @Column(type="string")
 */
private $address;

/**
 * @var string $comment
 * @Column(type="string")
 */
private $comment;

/**
 * @var integer $account_id
 * @Column(type="integer")
 */
private $account_id;

/**
 * @var integer $contact_id
 * @Column(type="integer")
 */
private $contact_id;

/**
 * @var string $created_at
 * @Column(type="string")
 */
private $created_at;

/**
 * @var contact_data $contact_data
 * @Column(name="contact_data", type="integer", nullable=false)
 * @OneToMany(targetEntity="Contact_Model_Contact", mappedBy="contact_data")
 * @JoinColumn(name="contact_id", referencedColumnName="id")
 */
private $contact_data;

... (getters and setters)

Model Contact

<?php
/**
 * @Table(name="contact_contacts")
 * @Entity(repositoryClass="Contact_Model_ContactRepository")
 */
class Contact_Model_Contact {

/**
 * @var integer $id
 * @Id @Column(type="integer") 
 * @GeneratedValue
 * @ManyToOne(targetEntity="Client_Model_Client", mappedBy="contact_data")
 */
private $id;

/**
 * @var string $name
 * @Column(type="string")
 */
private $name;

/**
 * @var string $email
 * @Column(type="string")
 */
private $email;

/**
 * @var string $phone
 * @Column(type="string")
 */
private $phone;

/**
 * @var integer $address
 * @Column(type="string")
 */
private $address;

/**
 * @var string $comment
 * @Column(type="string")
 */
private $comment;

/**
 * @var string $created_at
 * @Column(type="string")
 */
private $created_at;

/**
 * @var integer $contact_id
 * @Column(type="string")
 */
private $contact_id;

The query

    $qb = $this->_em->createQueryBuilder()
                ->select('i, o')
                ->from('Client_Model_Client', 'i')
                ->join('i.Contact_Model_Contact', 'o');
    $query = $qb->getQuery();
    $roles = $query->getResult();
    Zend_Debug::dump($roles); die;

What am I doing wrong? How should it work?

You should be doing this:

$qb = $this->_em->createQueryBuilder()
    ->select('i, o')
    ->from('Client_Model_Client', 'i')
    ->join('i.contact_data', 'o');