SonataUserBundle/Resources/config/doctrine/BaseUser.orm.xml

<?xml version="1.0" encoding="UTF-8"?>
<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
                  http://doctrine-project.org/schemas/orm/doctrine-mapping.xsd">

    <mapped-superclass name="Sonata\UserBundle\Entity\BaseUser">
        <field name="createdAt"    type="datetime"   column="created_at" />
        <field name="updatedAt"    type="datetime"   column="updated_at" />
        <field name="twoStepVerificationCode" type="string" length="255" column="two_step_code" nullable="true" />

        <lifecycle-callbacks>
            <lifecycle-callback type="prePersist" method="prePersist" />
            <lifecycle-callback type="preUpdate" method="preUpdate" />
        </lifecycle-callbacks>
    </mapped-superclass>

</doctrine-mapping>