.....
"require": {
    "php": ">=5.3.3",
    "symfony/symfony": "2.2.*",
    "doctrine/orm": "~2.2,>=2.2.3",
    "doctrine/doctrine-bundle": "1.2.*",
    "twig/extensions": "1.0.*",
    "symfony/assetic-bundle": "2.1.*",
    "symfony/swiftmailer-bundle": "2.2.*",
    "symfony/monolog-bundle": "2.2.*",
    "sensio/distribution-bundle": "2.2.*",
    "sensio/framework-extra-bundle": "2.2.*",
    "sensio/generator-bundle": "2.2.*",
    "jms/security-extra-bundle": "1.4.*",
    "jms/di-extra-bundle": "1.3.*",
    "friendsofsymfony/user-bundle": "*",
    "doctrine/doctrine-migrations-bundle": "dev-master",
    "stof/doctrine-extensions-bundle": "~1.1@dev"
},
....

stof_doctrine_extensions:
    default_locale: en_US
    orm:
        default:
            sluggable: true
            sortable: true

<?php

namespace SixStringPearBundleEntity;

use GedmoMappingAnnotation as Gedmo;
use DoctrineORMMapping as ORM;

/**
 * @ORMEntity
 * @ORMTable(name="icon")
 * @ORMHasLifecycleCallbacks()
 */
class Icon
{

....(other properties and getters/setters)

/**
 * @var datetime $created
 *
 * @GedmoTimestampable(on="create")
 * @ORMColumn(type="datetime")
 */
protected $created;

/**
 * @param datetime $created
 */
public function setCreated($created)
{
    $this->created = $created;
}

/**
 * @Route("/admin/go")
 */
public function goAction(){

    $icon = new SixStringPearBundleEntityIcon();
    $icon->setName("shawn");
    $icon->setZip(12345);
    $icon->setType("go");

    $em = $this->getDoctrine()->getManager();
    $em->persist($icon);
    $em->flush();
}

An exception occurred while executing 'INSERT INTO icon (name, zip, thumb, created, updated, createdBy_id) VALUES (?, ?, ?, ?, ?, ?)' with params ["shawn", 12345, "go", null, null, null]:

SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'created' cannot be null

stof_doctrine_extensions:
    orm:
        default:
            timestampable: true

stof_doctrine_extensions:
    default_locale: en
    translation_fallback: true
    orm:
        default:
            timestampable: true