[gentoo-user] pgo not selected for firefox 18

[Adam Carter]

17 compiled with pgo but in the emerge output for 18 it shows as (-pgo).
pgo is selected in make.conf, and in the ebuild;

DEPEND="${RDEPEND}
        dev-python/pysqlite
        virtual/pkgconfig
        pgo? (
                =dev-lang/python-2*[sqlite]
                >=sys-devel/gcc-4.5 )
        amd64? ( ${ASM_DEPEND}
                virtual/opengl )
        x86? ( ${ASM_DEPEND}
                virtual/opengl )"

And I have python 2 built with sqlite and gcc 4.7.2. Why is pgo not enabled?