Clamav won't update

[Robert S <robert.spam.me.senseless@gmail.com>]

I have the following in my /etc/apt/sources.list:

deb http://public.planetmirror.com/pub/debian-volatile/ sarge/volatile main

When I try to upgrade my system, it doesn't show that clamav will be upgraded:

# aptitude update && aptitude upgrade -s
Reading Package Lists... Done
Building Dependency Tree
Reading extended state information
Initializing package states... Done
Reading task descriptions... Done
Hit http://public.planetmirror.com sarge/volatile/main Packages
Hit http://public.planetmirror.com sarge/volatile/main Release
Reading Package Lists... Done
Building Dependency Tree
Reading extended state information
Initializing package states... Done
Reading task descriptions... Done
Reading Package Lists... Done
Building Dependency Tree
Reading extended state information
Initializing package states... Done
Reading task descriptions... Done
No packages will be installed, upgraded, or removed.
0 packages upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 0B of archives. After unpacking 0B will be used.
Would download/install/remove packages.

I've still got 0.85.1 installed:

# aptitude show clamav
Package: clamav
State: installed
Automatically installed: no
Version: 0.85.1-2

I've tried a mirror in Germany with the same result.
Can somebody explain?