Can't set metadata when using XeTex and pdfx to create a PDF/A file

I’m trying to create a PDF/A file using XeTex and leveraging the pdfx package. The page 96 of the pdfx documentation seems to indicate that XeTex should be accomodated.

I’ve also tried using xmpincl explicitly (it’s usually inherited by pdfx) but apparently that only works with pdflatex

If I comment out usepackage[a-1b]{pdfx} then I get the metadata as I expect, but then my output doesn’t conformed to PDF/A.

btw I’m using xelatex to embed fonts; a requirement for PDF/A… doing so in pdflatex was a real pain.

Any thoughts on how to get metadata in the PDF?

documentclass{book}

usepackage[a-1b]{pdfx}
usepackage{hyperref}

  hypersetup{
    pdftitle={This is the title},
    pdfauthor={This is the author},
    pdfcreator={This is the creator}}
    usepackage[main=english]{babel}

begin{document}
  This is some text
end{document}

Also, here is the output from xetex --version

XeTeX 3.14159265-2.6-0.99998 (TeX Live 2017/Debian)
kpathsea version 6.2.3
Copyright 2017 SIL International, Jonathan Kew and Khaled Hosny.
There is NO warranty.  Redistribution of this software is
covered by the terms of both the XeTeX copyright and
the Lesser GNU General Public License.
For more information about these matters, see the file
named COPYING and the XeTeX source.
Primary author of XeTeX: Jonathan Kew.
Compiled with ICU version 60.2; using 60.2
Compiled with zlib version 1.2.11; using 1.2.11
Compiled with FreeType2 version 2.8.1; using 2.8.1
Compiled with Graphite2 version 1.3.11; using 1.3.11
Compiled with HarfBuzz version 1.7.2; using 1.7.2
Compiled with libpng version 1.6.34; using 1.6.34
Compiled with poppler version 0.62.0
Compiled with fontconfig version 2.12.6; using 2.12.6