The Events Calendar Plugin: Hierarchical List of Upcoming Event Categories

I’m displaying a hierarchical list of categories from the Events Calendar plugin on this site (click “browse by category” to see it in action):

This is the code I’m using:

‘title_li’ => ”,
‘orderby’ => ‘name’,
‘order’ => ‘ASC’
wp_list_categories( $args );

The problem is that this shows all event categories, including from events that have passed. I need to show categories from upcoming events only.

Here’s some more info and some ideas on solutions:

Looking forward to hearing from somebody who can get this working! ?

Thanks in advance.