stream_resolve_include_path returning false?

I have a fieldset that is implementing InputFilterProviderInterface. My getInputFilterSpecification function looks like this:

public function getInputFilterSpecification() {
    $validator = new \Zend\Validator\File\Extension([
        'jpg',
        'jpeg',
        'png',
        'gif',
    ]);
    return [
        [
            'name' => 'logo',
            'required' => false,
            'validators' => [
                $validator,
            ],
        ],
    ];
}

As you can guess, I am trying to validate the file upload by extension.

My problem is that the validator is giving the error message

File is not readable or does not exist

Looking into the Extension class I found the function that's causing the issue: stream_resolve_include_path($file). When I var_dump $file I get the following output:

C:\Windows\Temp\php6BE7.tmp

So... Why is stream_resolve_include_path failing to resolve this path? How do I fix it?

This is currently running on a Windows Virtual Machine. Is this part of the problem? i.e. the above function only works on compatible operating systems?

Short term solution - extend the validator and overwrite the isValid function.

Find the line:

if (empty($file) || false === stream_resolve_include_path($file)) {

and replace it with:

if (empty($file) || false === is_file($file)) {