test/XInclude/docs/fallback6.xml

<?xml version="1.0"?>
<doc>
    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="b.xml">
        <xi:fallback><xi:include href="c.xml">
            <xi:fallback/>
        </xi:include></xi:fallback>
    </xi:include>
</doc>