native-comp error: Invalid function #<subr or>

[mousebot]

hi,

i maintain mastodon.el.

when i build it from a package archive, i get the following errors during 
native compiling:

Warning (comp): /path/to/.emacs.d/straight/build/mastodon/mastodon-tl.el: Error: 
Invalid function #<subr or>

it happens for two files in mastodon.el.

i'm unsure how to debug, or how to even understand this message. i'm also 
unable to reproduce it locally, or perhaps i just don't know how to native 
compile a package locally...

is anyone able to throw me any little bones/pointers?

thanks,
m