helm-completing-read-handlers-alist

[twiebke]

I wrote

(use-package org-books
  :ensure t
  :config
  (setq org-books-file "~/books/bücherliste.org"))

and get
Error (use-package): org-books/:catch: Symbol’s value as variable is void: helm-completing-read-handlers-alist

helm is installed.

What is to do to use org-books?