[racket] Scribble index missing when generating pdf file

Hi All.

The following document when rendered to HTML gives a nice index.
However when rendered to PDF the index page just has the "Index"
header, but the page is otherwise blank.

I use the buttons from within DrRacket to render to two formats.

What am I missing?

#lang scribble/base
@title{Testing index}
@section{First section}
@subsection{A subsection of the first section}
Some @as-index{text}.
@section{Second section}
@(index-section)

/Jens Axel