C stack overflow when loading modus themes

(setq modus-vivendi-theme-slanted-constructs t)
(setq modus-vivendi-theme-bold-constructs t)
(setq modus-vivendi-theme-fringes 'subtle)
(setq modus-vivendi-theme-faint-syntax nil)
(setq modus-vivendi-theme-no-mixed-fonts nil)
(setq modus-vivendi-theme-completions 'moderate)
(setq modus-vivendi-theme-diffs 'desaturated)
(setq modus-vivendi-theme-intense-paren-match t)
(load-theme 'modus-vivendi t)

This results in the error Re-entering top level after C stack overflow at startup. I'm not sure how to debug this as toggle-debug-on-error has no effect on C code. Using manoj-dark as the theme works just fine.

This is on GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.23, cairo version 1.16.0) of 2020-10-20, unofficial emacs-snapshot build: http://emacs.secretsauce.net and I am using the built-in modus themes, not from melpa.