Call to undefined method Symfony\Component\Validator\ExecutionContext::getValidator()

Receiving this error when using PHP 5.5.9 & Silex 1.2 FormServiceProvider & ValidationServiceProvider when using $form->handleRequest($request) with a non-empty Request object, this had been working in <= Symfony 2.5.2

( ! ) Fatal error: Call to undefined method Symfony\Component\Validator\ExecutionContext::getValidator() in /var/www/vendor/symfony/form/Symfony/Component/Form/Extension/Validator/Constraints/FormValidator.php on line 56
Call Stack

Time Memory Function Location

1 0.0001 247648 {main}( ) ../index.php:0
2 0.0315 535248 Silex\Application->run( ) ../index.php:567
3 0.0343 617168 Silex\Application->handle( ) ../Application.php:515
4 0.0476 722528 Symfony\Component\HttpKernel\HttpKernel->handle( ) ../Application.php:538
5 0.0476 723024 Symfony\Component\HttpKernel\HttpKernel->handleRaw( ) ../HttpKernel.php:66
6 0.0594 905392 call_user_func_array:{/var/www/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/HttpKernel.php:145} ( ) ../HttpKernel.php:145
7 0.0595 906120 {closure:/var/www/web/index.php:33-54}( ) ../HttpKernel.php:145
8 0.1315 1705224 Symfony\Component\Form\Form->handleRequest( ) ../index.php:35
9 0.1315 1705856 Symfony\Component\Form\Extension\HttpFoundation\HttpFoundationRequestHandler->handleRequest( ) ../Form.php:488
10 0.1315 1708016 Symfony\Component\Form\Form->submit( ) ../HttpFoundationRequestHandler.php:80
11 0.1331 1727384 Symfony\Component\EventDispatcher\ImmutableEventDispatcher->dispatch( ) ../Form.php:655
12 0.1331 1727384 Symfony\Component\EventDispatcher\EventDispatcher->dispatch( ) ../ImmutableEventDispatcher.php:42
13 0.1331 1727384 Symfony\Component\EventDispatcher\EventDispatcher->doDispatch( ) ../EventDispatcher.php:53
14 0.1331 1727736 call_user_func:{/var/www/vendor/symfony/event-dispatcher/Symfony/Component/EventDispatcher/EventDispatcher.php:164} ( ) ../EventDispatcher.php:164
15 0.1331 1727776 Symfony\Component\Form\Extension\Validator\EventListener\ValidationListener->validateForm( ) ../EventDispatcher.php:164
16 0.1331 1727856 Symfony\Component\Validator\Validator->validate( ) ../ValidationListener.php:64
17 0.1369 1753688 Symfony\Component\Validator\ValidationVisitor->validate( ) ../Validator.php:101
18 0.1369 1754752 Symfony\Component\Validator\Mapping\ClassMetadata->accept( ) ../ValidationVisitor.php:167
19 0.1369 1754960 Symfony\Component\Validator\ValidationVisitor->visit( ) ../ClassMetadata.php:157
20 0.1375 1773376 Symfony\Component\Validator\ExecutionContext->validateValue( ) ../ValidationVisitor.php:112
21 0.1375 1773736 Symfony\Component\Validator\ExecutionContext->executeConstraintValidators( ) ../ExecutionContext.php:240
22 0.1442 1788872 Symfony\Component\Form\Extension\Validator\Constraints\FormValidator->validate( ) ../ExecutionContext.php:275