Renaming the old ebuild seems to work. Reproducible: Always
+*workrave-1.9.4 (08 Jun 2011) + + 08 Jun 2011; Pacho Ramos <pacho@gentoo.org> -workrave-1.9.1-r1.ebuild, + -workrave-1.9.2.ebuild, +workrave-1.9.4.ebuild: + Version bump, remove old. +
Sorry, I forgot credits for you in changelog entry :-S Anyway, thanks a lot for notifying the bump