M-$ or ispell-word works by default but C-M-i or ispell-complete-word fails.

Steps to reproduce the error
 - emacs -Q
 - C-x b xxx
 - M-x text-mode
 +
 - type "ju"
 - C-M-i ;;=> causes the echo area to say the following

> ispell-lookup-words: lookup-words error: No plain word-list found at
> systemdefault locations.  Customize ‘ispell-alternate-dictionary’ to
> set yours.

The unexpected behavior is the above error shown in the *Messages* buffer.

The expected behavior is similar to the result from M-$ or ispell-word providing a list of options to choose.

A workaround I have found is as follows
 - at the shell command line
 - $ aspell -l en dump master > en-word-list
 - $ sort en-word-list > en-sorted-word-list
 +
 - customize:ispell-complete-word-dict to read the file "path/to/en-sorted-word-list"
 - C-M-i on "ju" then generates a listing of word options

See attached file bug-gnu-emacs--report.text