unstable in virtualbox on testing + higher resolutions

[Felix Natter <fnatter@gmx.net>]

hi,

I cannot configure my current unstable (guest) in a-week-old testing
(host using virtualbox) to more than 1024x768. I guess I need
"virtualbox-guest-x11" for that, but it doesn't install on current
unstable:

felix@debianunstable:~$ sudo apt-get install virtualbox-guest-x11
[sudo] password for felix: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 virtualbox-guest-x11 : Depends: xorg-video-abi-15 but it is not installable
E: Unable to correct problems, you have held broken packages.

https://packages.debian.org/sid/virtualbox-guest-x11
looks ok, and xserver-xorg-core 2:1.16.0-1 is installed.

Any idea what I'm doing wrong?

Thanks and Best Regards,
-- 
Felix Natter