Update Problem from 1.04 to 1.05

Hi, trying to upate to the latest versions raises the following error:
mod_fcgid: stderr: PHP Fatal error: Call to undefined method Grav\Common\GPM\Upgrader::meetsRequirements() in (path removed)/user/plugins/admin/classes/gpm.php on line 182, referer: (path removed)admin
Any ideas, what is causing this? I am running an a Debian Wheezy fully updated. The previous updates worked without problems.
Thanks for your help!

Hi, can you update Grav core, from admin or from the command line? I think the problem is you updated first Admin, which calls a method only added in the latest Grav

Hi,
thanks a lot for your help! Yes, that worked. Just pressed "Update all" in the admin panel, but didn't think about the admin update!
Thanks again for your fast help!