[CentOS] yum priorities question

Hello,

I have a question about working principles of yum.

Here are the details:

Installed package: GeoIP.i386 1.4.4-1.el5.centos
Repo: CentOS Extras
Priority for CentOS Extras repo: 1

"yum update" wants to replace the above package with the following:

Package: geoip.i386 1.4.5-1.el5.rf
Repo: rpmforge
Priority for rpmforge: 15

And yes, the following is already in the priorities.conf
[main]
enabled=1

Why does yum try to replace the package from a repo with higher 
priority? Isn't "yum priorities" supposed to keep it?

Regards,
Mufit