Compilation error

[HTV04]

So I've been trying to compile zepto8, and I managed to compile it up to these errors:

In file included from pico8/cart.h:21,
                 from player.h:21,
                 from zepto8.cpp:23:
./pico8/memory.h:315:27: error: member ‘z8::pico8::custom_font_t z8::pico8::memory::<unnamed union>::<unnamed struct>::custom_font’ with constructor not allowed in anonymous aggregate
  315 |             custom_font_t custom_font;
      |                           ^~~~~~~~~~~
./pico8/memory.h:315:27: error: member ‘z8::pico8::custom_font_t z8::pico8::memory::<unnamed union>::<unnamed struct>::custom_font’ with copy assignment operator not allowed in anonymous aggregate

I noticed that the file throwing the error has this note about nameless unions... before the nameless union that is seemingly causing the error. https://github.com/samhocevar/zepto8/blob/9d7a6d49f13f50387089df6e9c00fb3fb84c8019/src/pico8/memory.h#L297-L298

Am I doing something wrong? I can't really find anything useful online about this weird error, so I didn't bother trying to change any code.