Add listing page doesn't show excerpt – short description

I use Business Directory theme 8.1 (version 2015-03-19). I want my customers to be able to add excerpts to show on the search results page, but the add-listing page doesn’t have them.

This also happens in the demo. According to other people’s questions, seems like it used to be there, and people still want it:
Add listing page problems
Listings and add listings page admin.

Looking in the source code, seems it’s not there at all:
[code title=”tpl-add.php”]
case “2”: { // LISTING DESCRIPTION
// stuff about post_title, post_content, post_tags – nothing about post_excerpt
[/code]

I guess I could hack something in there, but I don’t want to edit the theme – I’ll overwrite once I upgrade…