PHP Fatal error: Class Drupal\Driver\DrushDriver contains 1 abstract method

I have just updated my drupal extension using composer.phar update and now when I run bin/behat I get the following error. I am just tring to get my head around Behat and Mink but I will see if I can help

PHP Fatal error:  Class Drupal\Driver\DrushDriver contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (Drupal\Driver\DriverInterface::termDelete) in {projectdir}/vendor/drupal/drupal-extension/src/Drupal/Driver/DrushDriver.php on line 209

php --version PHP 5.4.9-4ubuntu2.1 (cli) (built: Jun 11 2013 13:08:51) 

contents of my composer.json

{
  "require": {
      "drupal/drupal-extension": "*"
    },
  "minimum-stability": "dev",
  "config": {
      "bin-dir": "bin/"
    }
}

behat.yml

default:
    paths:
        features: 'features'
    extensions:
        Behat\MinkExtension\Extension:
            goutte: ~
            selenium2: ~
            base_url: http://localhost/
            default_session: "goutte"
            javascript_session: "selenium2"
        Drupal\DrupalExtension\Extension:
            blackbox: ~
            drush:
                alias: local

composer.lock attached as composer.txt