[racket] message-box too small to display title

Matthew wrote:
> As for the big icon within the `message-box' dialog, that a common
> convention, although you have to specify something like
> MB_ICONEXCLAMATION for MessageBox() to enable it on Windows. The Racket
> `message-box' dialog defaults to an application-specific icon, which I
> guess is a Mac OS X convention, but you can override it with a 'caution
> or 'stop style. There's no icon in the title bar for `message-box'
> because it's a dialog, and Windows dialogs normally do not have an
> title-bar icon.
>

How do I get rid of the icon in the message-box text area.

Thanks,
Harry