Control: tags -1 fixed-upstreamAfter discussion with the previous maintainer of wmgtemp, maintenance has transferred to the Window Maker Team.
A new upstream version (1.2) has been released which fixes this bug [1].I have prepared a new Debian package [2], but will wait until after Stretch is released to upload.
[1] http://www.dockapps.net/wmgtemp[2] https://anonscm.debian.org/git/pkg-wmaker/wmgtemp.git/commit/?id=f6dc7a9