When qt4 is selected to be the default Qt version via dev-qt/qtchooser, mkvtoolnix's configuration script can not find Qt5. Trivial fix is to add use qt5 && export QT_SELECT=qt5 to the ebuild src_configure() Reproducible: Always Steps to Reproduce: 1. # ln -sf /etc/xdg/qtchooser/qt4.conf /etc/xdg/qtchooser/default.conf 2. USE="qt5" emerge -1 media-video/mkvtoolnix
until this is fixed you can simply mkdir /etc/portage/env/media-video echo "export QT_SELECT=qt5" > /etc/portage/env/media-video/mkvtoolnix
+ 31 Jan 2015; Ben de Groot <yngwin@gentoo.org> mkvtoolnix-7.5.0.ebuild: + Point directly to Qt5 tools to fix bug #532600, and actually build + experimental mkvtoolnix-gui. It still doesn't install a desktop file though.