+Cc sox-devel.

Joonun: thank you for reporting, the following patch should fix
the problem.  I guess make sure sox-devel knows about any other
bugs you find; original upstream developers seem to busy so it's
mostly Måns and I.  I don't think either of us have permission
to the SourceForge.net project; either...

Will also try to look at https://bugs.debian.org/881121 soon
(maybe Måns can help).