Hi all, I've tried to open an attached file (added with org-attach-attach), however, when I try to open it with C-c C-o I got the following backtrace: #+begin_example Debugger entered--Lisp error: (wrong-number-of-arguments (2 . 2) 1) org-attach-follow("1805.00020.pdf") org-link-open((link (:type "attachment" :path "1805.00020.pdf" :format bracket :raw-link "attachment:1805.00020.pdf" :application nil :search-option nil :begin 717 :end 818 :contents-begin 746 :contents-end 816 :post-blank 0 :parent (paragraph (:begin 717 :end 819 :contents-begin 717 :contents-end 819 :post-blank 0 :post-affiliated 717 :parent (item (:bullet "- " :begin 708 :end 819 :contents-begin 717 :contents-end 819 :checkbox off :counter nil :structure (... ... ... ... ...) :pre-blank 0 :post-blank 0 :post-affiliated 708 :tag nil :parent (plain-list ...))))))) nil) org-open-at-point(nil) funcall-interactively(org-open-at-point nil) call-interactively(org-open-at-point nil nil) command-execute(org-open-at-point) #+end_example After adding =&optional= to the definition of =org-attach-follow=, and reloading org-mode (uncompiled) I could get through org-attach-follow. But, then I hit another issue: #+begin_example Debugger entered--Lisp error: (void-function org-link-open-as-file) (org-link-open-as-file (org-attach-expand file) arg) org-attach-follow("0906.4487.pdf") … #+end_example After an =eval-defun= on =org-link-open-as-file=, I finally could open my attachment. I used =emacs -q=, installed org freshly and used a clean org-file with only a single header entry and the attachment to reproduce my issue. Cheers, Simon Braß Emacs : GNU Emacs 27.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.22, cairo version 1.17.3) of 2020-08-28 Package: Org mode version ( @ /home/sbrass/.emacs.d/elpa/org-9.4.4/)