[plt-scheme] Is UNICODE in the code taboo?

On Thu, Dec 11, 2008 at 3:53 AM, Pierpaolo Bernardi <olopierpa at gmail.com> wrote:
> Even better, put:
>
> (set-language-environment 'utf-8)
>

My C-h f on set-language-environment says that the input must be a
string. Does that vary from version to version of Emacs?

Thanks,
Robby