Epigraph for parts

The document that I am preparing in Docbook 5 has an epigraph following
the part title. My XML editor is reporting that <epigraph> cannot occur
immediately inside <part>, only inside <chapter>. Is this really the
case?  Considering how common it is for books to have epigraphs on a new
part title page, this seems like a serious deficiency.

What workaround would the community propose? Putting epigraph after the
first chapter tag would not work, as that chapter already has its own
epigraph.