public function afterPrepare(Event $event)
	{
		$command = $event['command'];
		$operation = $command->getOperation();

		if ($command->offsetExists('_kmd')) $command->offsetUnset('_kmd');
		if ($command->offsetExists('_acl')) $command->offsetUnset('_acl');

		if ($operation->getName() !== 'createEntity' && $command->offsetGet('collection') === 'user')
		{
			// These values should never be passed to Kinvey on a user update operation.
			if ($command->offsetExists('username')) $command->offsetUnset('username');
			if ($command->offsetExists('password')) $command->offsetUnset('password');
			if ($command->offsetExists('salt')) $command->offsetUnset('salt');
		}
	}