How do I remove unused embedded fonts?

I have an odt file with embedded fonts that is around 25MB in size, despite being just one simple page. Unzipping the file I can see it is embedding the Arial and SimSun fonts that are not used in the document.

I’ve examined the XML to try to work out where it thinks it’s being used and found the following:

<style:text-properties fo:font-variant="normal" fo:text-transform="none" fo:color="#729fcf" style:text-outline="false" style:text-line-through-style="none" style:text-line-through-type="none" style:font-name="Humanst531 UBlk BT" fo:font-size="84.5pt" fo:font-style="normal" fo:text-shadow="none" style:text-underline-style="none" fo:font-weight="normal" style:letter-kerning="true" style:font-name-asian="Microsoft YaHei" style:font-size-asian="84.5pt" style:font-style-asian="normal" style:font-weight-asian="normal" style:font-name-complex="Arial1" style:font-size-complex="84.5pt" style:font-style-complex="normal" style:font-weight-complex="normal" style:text-emphasize="none" style:font-relief="none" style:text-overline-style="none" style:text-overline-color="font-color"/>

Is there any way I can remove these fonts from my file to bring it to a much more sensible size? Do I need to manually edit the XML and zip it back up?

Looks like this is a known bug:

https://bugs.documentfoundation.org/show_bug.cgi?id=65353