NaN?

Hello
I define:

<xsl:decimal-format grouping-separator="'" decimal-separator="." 
name="CHF" NaN="ouch"/>
In the XML there are attributes like:

<jahr datum="2019" einzahlung="" auszahlung="" kumuliert="141000" 
garantiert="" mittel="131209"/>
<fo:block>
 <xsl:value-of select="format-number(@einzahlung,CHF)"/>
</fo:block>

but in my PDF there are still these "Nan"s instead of the "ouch".
what i'm doing wrong?


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