sort a repeater with content custom

I thought it was possible, so I guess I'm just doing something wrong?

I have a repeater called 'images' (id=images) that contains images and their title/name (id=name). They are in a specific order that I use to display them, but I also want a list on the side in alphabetical order. But that doesn't seem to work...

<?php
    perch_content_custom('collection', array(
        'template'=>'template_collection_list.html',
        'sort'=>'images.name',
        'sort-order'=>'ASC'
    )); 
?>

Template:

<perch:repeater id="images" label="Images" scope-parent="true">
    <perch:before>
        <dt><perch:content type="text" id="parent.title" label="Name collection" required="true" title="true" /></dt>
    </perch:before>

    <dd><a href="#<perch:content id="nameslug" type="slug" for="name" />"><perch:content type="text" id="name" label="Name dress" /></a></dd>
</perch:repeater>

Does anyone see what I'm doing wrong?