When two or more modules define the following definition the method (factory) becomes incorrectly uncallable...

return array(
    'di' => array(
        'definition' => array(
            'class' => array(
                'Zend\Cache\Storage\Adapter\Filesystem' => array(
                    'instantiator' => array(
                        'Zend\Cache\StorageFactory',
                        'factory',
                    ),
                ),
            ),
        ),
    ),
);

 
Fatal error: Uncaught exception 'RuntimeException' with message 'Invalid instantiator: Zend\Cache\StorageFactory::factory() is not callable.' in /vendor/ZendFramework/library/Zend/Di/Di.php:198

On investigation is seems the 'instantiator' array is merged incorrectly, as it contents will be the following, which is indeed not a valid PHP callback.

Array
(
    [0] => Zend\Cache\StorageFactory
    [1] => factory
    [2] => Zend\Cache\StorageFactory
    [3] => factory
)

I am unsure how to resolve such a configuration. Should DI assume the first two keys as correct?