Dynamic NextJS sitemap, xml extension stripped on XDN

We have a dynamic sitemap page that lives at pages/sitemap.xml.tsx. This page renders exactly as expected locally and when building, it looks to be built properly:

Screen Shot 2021-04-21 at 4.07.46 PM

However, once it hits the XDN (using xdn run --production) the xml extension is not present and the route can only be reached at /sitemap, not /sitemap.xml.

Screen Shot 2021-04-21 at 4.08.04 PM

We can have robots.txt look at /sitemap for now, but would prefer if we could use the proper extension.

Let us know what other details we can provide!