Getting attachments by meta value

I’m stuck at a very simple point: I need to get all attachments by a custom meta key (and value). I’m developing a short code, so it has to work on every possible page.

What I’ve tried so far:

$args = array(
    'post_type' => 'attachment',
    'meta_query' => array(
        array(
            'key' => 'medientyp',
            'value' => 'Video'
        )
    )
);
$query = new WP_Query($args);

But that does not find anything (yes, there do entries exist.)

Did I get something wrong? Or do I miss something?

I’ve spent hours of research and found the solution a few minutes after writing this question:

$args = array(
    'post_type'   => 'attachment',
    'post_status' => 'inherit',       <<-- IMPORTANT
    'meta_query'  => array(
        array(
            'key'     => 'medientyp',
            'value'   => 'Video'
        )
    )
);
$query = new WP_Query($args);