I have a problem with following key binding:

(global-set-key (kbd "C-/") 'comment-or-uncomment-region)

Actually, it is ignored by Emacs so undo is executed instead. I'm running Emacs in gui mode.

  • 2
    Do you have any minor-modes active such as undo-tree, which would override global bindings? Type M-x describe-key or C-h k and then your keyboard shortcut and verify that the actual function being called is exactly undo or something else. Also, check your *Messages* buffer for error messages after starting Emacs -- an error in the init file can cause Emacs to stop loading the file once it reaches that particular point.
    – lawlist
    Nov 27, 2017 at 18:47
  • It works for me. Do you see the same thing if you start Emacs using emacs -Q (no init file)? If not, recursively bisect your init file to find the culprit.
    – Drew
    Nov 27, 2017 at 18:51
  • Yes, i have undo tree.
    – dev1223
    Nov 27, 2017 at 19:18
  • Not sure what's causing this, but maybe Emacs is not-so-subtly telling you to just use the M-; binding which does what you want by default already.
    – Stefan
    Nov 28, 2017 at 13:40

1 Answer 1


Thanks to describe-key, I found that / is interprpeted as a <kp-divide>, so this keybind is working like a charm now. (thanks lawlist)

(global-set-key (kbd "C-<kp-divide>") 'comment-or-uncomment-region) 

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