SonataAdminBundle/Resources/config/twig.xml

<?xml version="1.0" encoding="UTF-8" ?>

<container xmlns="http://symfony.com/schema/dic/services"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">

    <services>
        <service id="sonata.admin.twig.extension" class="Sonata\AdminBundle\Twig\Extension\SonataAdminExtension">
            <tag name="twig.extension"/>

            <argument type="service" id="sonata.admin.pool" />
        </service>
    </services>
</container>