I can confirm this bug, i guess xcomposite.pc should be in /usr/lib/pkgconfig/ and not /usr/X11R6/lib/pkgconfig At the moment pkg-config doesnt find xcomposite.pc so configure script (for xfwm package) doesnt find it. Exporting PKG_CONFIG_PATH is a workaround (which should work even in debian/rules file for xfwm4 package) but it's only a workaround. Would it be possible to move this file ? Regards, -- Yves-Alexis Perez