主义乐观锁定

I am having a problem with doctrine optimistic locking.

I have mapped my entity like the documentation says (I guess I think so), and my optimistic locking version doesn't increment. It always stays as null inside the database.

Part of my entity and it's mapping:

Entity:

/** @var  AccountID */
private $accountID;

/** @var ClientID  */
private $clientID;

/** @var Money  */
private $money;

/** @var  array|Transfer[] */
private $transfers;

/** @var  bool Account status - active not active */
private $active;

/** @var  int */
private $version = 1;

Mapping:

<doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping
               https://raw.github.com/doctrine/doctrine2/master/doctrine-mapping.xsd">

<entity name="Madkom\ES\Banking\Domain\Account\Account" table="account">

    <indexes>
        <index name="client_id_idx" columns="client_id"/>
    </indexes>

    <embedded name="accountID" class="Madkom\ES\Banking\Domain\Account\AccountID" />
    <embedded name="clientID" class="Madkom\ES\Banking\Domain\Account\ClientID" />
    <embedded name="money" class="Madkom\ES\Banking\Domain\Money" />
    <field name="transfers" column="transfers" type="jsonb"/>
    <field name="active" column="active" type="boolean" length="32" unique="true" />
    <field name="version" type="integer" version="true"/>

</entity>

Whenever I added new record, version is always the same, null. I am using Postgresql 9.4 and Doctrine 2.5.1. The jsonb type comes from outside library.