Numbering book parts & appendices broken in xsl 1.69?

Hi,

I found a strange behavior after upgrading from docbook-xsl 1.68.1 to 1.69:

I haven't customized anything with the numbering style. With 1.68.1 the parts 
got labeled with roman numbers (I., II., ...) and the appendices with letters 
(A., B.,...).

With 1.69 parts and appendices are labeled with numbers (1., 2.,...).

I tried to work around that problem with this customisation code:

<xsl:template match="part" mode="division.number">
  <xsl:number from="book" count="part" format="I."/>
</xsl:template>

but it didn't help.

Is this a bug is 1.69 or a problem on my side?

Kind regards,

Gerd