Error with nobreak/fontfit

[pgundlach]

<Layout xmlns="urn:speedata.de:2009/publisher/en"
    xmlns:sd="urn:speedata:2009/publisher/functions/en"
    version="4.19.31">
    <Trace grid="yes" />
    <Record element="data">
        <PlaceObject>
            <Textblock width="5">
                <Paragraph>
                    <NoBreak reduce="fontfit">
                        <B>
                            <Value select="'The quick brown fox jumps over the'" />
                        </B>
                    </NoBreak>
                </Paragraph>
            </Textblock>
        </PlaceObject>
    </Record>
</Layout>

Has no effect.