Error on DocBook's linegroup (fo:list-item-label is missing child elemens)

Question

I am experimenting with DocBook → FO→ PDF conversion (new to DocBook). fop fails on <linegroup> (on the MWE below) with:

"fo:list-item-label" is missing child elements. Required content model: marker* (%block;)+

The commands I run are these two (docbook-xml-ns 1.79.2 and fop 2.6-2, packaged for Debian stable):

xsltproc -o db0.fo /usr/share/xml/docbook/stylesheet/docbook-xsl-ns/fo/docbook.xsl db0.xml
fop -pdf db0.pdf -fo db0.fo

And this is the db0.xml, minimal input for xsltproc.

<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook V5.2//EN" "http://www.oasis-open.org/docbook/xml/5.2/docbook.dtd">
<book xmlns="http://docbook.org/ns/docbook" version="5.2">
    <chapter>
        <linegroup>
            <line>Line 1</line>
            <line>Line 2</line>
        </linegroup>
    </chapter>
</book>

Could someone point me in the direction of fixing this?

I need the <linegroup> (or anything similar) to quote a fragment written in verse, and can't use <literallayout> as the lines contain markup (footnote, emphasis etc).