dimmer-face-color: Wrong type argument: stringp, reset

[AnweshGangula]

I'm trying to use dimmerr with :foreground adjustment mode, but it's causing error - dimmer-face-color: Wrong type argument: stringp, reset. The same config works fine with :background mode without any other change. Below is my config:

(use-package dimmer
  :config
  (setq dimmer-adjustment-mode :background)
  (setq dimmer-fraction 0.3)
  (add-to-list 'dimmer-exclusion-regexp-list "^\\*imenu-list\\*$")
  (setq dimmer-use-colorspace :rgb)
  (dimmer-mode t))

[timmli]

Same here since upgrading to Emacs v29.