@gamburg.m No idea. But … try updating to 8.6 (or 8.5) and see if the error is gone.

Note: The new 8.6 is ready for download, but there is a small delay - so http://docs.racket-lang.org\|docs.racket-lang.org still shows 8.5 docs.

<https://download.racket-lang.org/>

Good idea, that’s giving me a much better error message, thanks!

My guess is that it was a problem with the expander not tracking dependencies well enough, and it got confused by an old cached compile. Upgrading might trigger a suitable recompile because the Racket version changed. If I’m guessing right, deleting a “compiled/cache” directory would also reset.