It seems to has been fixed upstream in http://svn.gnu.org.ua/viewvc/tex4ht/trunk/lit/tex4ht-4ht.tex?view=log#rev141 rev 141.
I have this problem too but I tried to patch it and it doesn't seems to be enough (patch: https://gist.github.com/rhaamo/4e6241ce44acbbcc89c564445b63bd82)
It seems to has been fixed upstream in http:// svn.gnu. org.ua/ viewvc/ tex4ht/ trunk/lit/ tex4ht- 4ht.tex? view=log# rev141 rev 141.
I have this problem too but I tried to patch it and it doesn't seems to be enough (patch: https:/ /gist.github. com/rhaamo/ 4e6241ce44acbbc c89c564445b63bd 82)