Nginx on Runcloud

I’m trying to get this to work on runcloud (running nginx/apache). Here’s the nginx config for runcloud: https://runcloud.io/docs/cheat-sheet/nginx.html#nginx-location

I tried to add the custom nginx snippet from the docs to /etc/nginx-rc/conf.d/my-app.d/main.conf and reload, but in that case the content-type became image/html. Does anyone have any ideas?