Fedora 18 changes the way how to work with services in spec files. It introduces new macros - %systemd_post, %systemd_preun and %systemd_postun; which replace scriptlets from Fedora 17 and older (see https://fedoraproject.org/wiki/Packaging:ScriptletSnippets#Systemd, https://bugzilla.redhat.com/show_bug.cgi?id=850016).
not sure when I added this but it has been added...