modus-themes-headings and non-nil value: examples from the manual are not working

Hello Prot,

sorry to bother you again...

I tried the following examples from the manual:

When defining the styles per heading level, it is possible to pass a non-nil value (t) instead of a list of properties. This will retain the original aesthetic for that level. For example:

(setq modus-themes-headings
      (quote ((1 . t)           ; keep the default style
              (2 . (semibold 1.2))
              (t . (variable-pitch))))) ; style for all other headings

(setq modus-themes-headings
      (quote ((1 . (variable-pitch extrabold 1.5))
              (2 . (semibold))
              (t . t)))) ; default style for all other levels

Both are resulting in this error when loading modus-themes:

internal-macroexpand-for-load: Eager macro-expansion failure: (wrong-type-argument listp t)

I had this problem with both versions: the latest from melpa, but also with 4.2.0 (the manual refers to 4.2.0).