### Improper `\hyphenation` will be flushed

For example

    ! Improper \hyphenation will be flushed.
    \'#1->{
           \accent 19 #1}
    <*> \hyphenation{Ji-m\'e
                            -nez}

(in Plain TeX) or

    ! Improper \hyphenation will be flushed.
    \leavevmode ->\unhbox
                          \voidb@x
    <*> \hyphenation{Ji-m\'e
                            -nez}

in LaTeX.

As mentioned in "hyphenation failures", words with accents in them may not be hyphenated. As a result, any such word is deemed improper in a `\hyphenation` command.

The solution is to use a font that contains the character in question, and to express the `\hyphenation` command in terms of that character; this "hides" the accent from the hyphenation mechanisms. LaTeX users can be achieved this by use of the fontenc package (part of the LaTeX distribution). If you select an 8-bit font with the package, as in `\usepackage[T1]{fontenc}`, accented-letter commands such as the `\'``e` in `\hyphenation{Ji-m\'``e-nez}` automatically become the single accented character by the time the hyphenation gets a to look at it.