Completion not working

I am running Emacs 29.4 and Chicken Scheme 5.4 under Arch Linux.

To try and reproduce my problem as simply as possible, I run emacs -Q then evaluate the following:

(require 'package)
(add-to-list 'package-archives '("melpa" . "https://melpa.org/packages/") t)
(package-initialize)

(when (not (package-installed-p 'use-package))
  (package-refresh-contents)
  (package-install 'use-package))

(require 'use-package)

(use-package geiser-chicken
  :ensure t
  :config (setq geiser-chicken-binary "chicken-csi"))

If I then open a scheme file, run a geiser reply and begin typing, e.g. (imp, then press C-M-i to invoke completion-at-point I get the following error: geiser-completion--symbol-list: Wrong type argument: listp, Error:

I have tried removing and re-installing both the geiser and geiser-chicken packages in Emacs, as well as removing and re-installing Chicken. I have followed the instructions for installing geiser-chicken (installing various required eggs, etc.)

This was working for me in the past, but something has evidently changed since I last used geiser/geiser-chicken. I had initially assumed it was a problem with corfu (the completion framework I usually use) but my minimal example above would suggest that it might be something to do with geiser.

Any help appreciated.