Indexterm with Umlaut rendered in the symbol division

Dear all,
when trying to transform indexterms with german Umlauts like

<section>
<title>
...
	<indexterm>
		<primary>鈁ersicht</primary>
		<secondary>nutzen</secondary>
	</indexterm>

using the auto index of the fo-stylesheets (one of the latest snaphshots), they are rendered in the Symbol-Division of the index. If I use "Uebersicht" instead everything works fine. So I guess this might be a bug in the autoidx.

Thanks and best wishes.
Ludger Thomas