ispell-init-process fails

When I try to correct a word with ispell, I got the following error:

ispell-init-process: Error: The encoding "nil" is not known. This could also mean that the file "/nix/store/pj0ivrsxk2hik5hv7pdywdxxga0m1wvv-aspell-0.60.8/lib/aspell/nil.cset" could not be opened for reading or does not exist.

I dug into this a bit. ispell-init-process internally sets variable ispell-library-directory

        (setq ispell-library-directory (ispell-check-version)
              ;; Assign a non-nil value to ispell-process-directory
              ;; before calling ispell-start-process, since that
              ;; function needs it to set default-directory when
              ;; ispell-async-processp is nil.
          ispell-process-directory default-directory
          ispell-process (ispell-start-process)
          ispell-filter nil
          ispell-filter-continue nil)

The full source code here

and I confirmed that this is indeed nil on my Emacs.

I guess this is because (ispell-check-version) returns nil. But I don't have a good idea why that happens. Could someone give me pointers, or any idea why this happens?

The definition of (ispell-check-version) here

Some more info

  1. aspell exists in the $PATH and Emacs can see it
(executable-find "aspell") => "/nix/store/lzphgp0k1cm7sz27f59jqaa57r13mlc2-aspell-env/bin/aspell"
  1. aspell version seems correct:
$ aspell -vv
@(#) International Ispell Version 3.1.20 (but really Aspell 0.60.8)
  1. Dictionaries seem available
$ aspell dump dicts
  1. I'm using DoomEmacs doom/version below:
GNU Emacs     v28.2            nil
Doom core     v3.0.0-pre       HEAD -> master, origin/master, origin/HEAD b66ad7703 2023-03-17 00:33:32 -0400
Doom modules  v23.03.0-pre     HEAD -> master, origin/master, origin/HEAD b66ad7703 2023-03-17 00:33:32 -0400
  • In my setup (using aspel 0.60.8 as well), my ispell-library-directory is also nil and (ispell-check-version) returns nil and yet I don't have any problem checking a word.
    – NickD
    Commented Mar 22, 2023 at 2:23
  • That's good to know! Indeed I found that ispell-library-directory does not need to be set if ispell-async-processp is non-nil. Commented Mar 23, 2023 at 2:22
  • @NickD Could you also tell me what you get when you evaluate (ispell-get-coding-system)? I got nil and am wondering if that's the issue. Commented Mar 23, 2023 at 2:27
  • I get utf-8, coming from (assoc ispell-current-dictionary ispell-dictionary-alist) which returns (nil "[[:alpha:]]" "[^[:alpha:]]" "[']" nil ("-B") nil utf-8).
    – NickD
    Commented Mar 23, 2023 at 4:08

1 Answer 1


Actually just adding this to a config file (In my case ~/.doom.d/config.el) solved it.

(after! ispell
  (setq ispell-dictionary "en_US")
  (setq ispell-local-dictionary "en_US")
  (setq ispell-local-dictionary-alist
        '(("en_US" "[[:alpha:]]" "[^[:alpha:]]" "[']" nil ("-d" "en_US") nil utf-8)

I was expecting either ispell-dictionary or ispell-local-dictionary-alist to be set automatically.

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