https://bugs.gentoo.org/show_bug.cgi?id=414371 Can confirm this bug. Sorry, if it's in wrong section, I didn't found better. It just complicating my way to Weston :-)
Fixed (well, worked around): http://cgit.freedesktop.org/xorg/lib/libxkbcommon/commit/?id=734be500
Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.