xz support in dpkg

[Andreas Balser <a@abalser.de>]

Hi,
I am running debian unstable, but upgrading only occasionally.
Now I have some packages which give an error message saying that dpkg
cannot handle "data.tar.xz". 

apt-get does not do much else than complaining about this, whatever I try to do.

Any ideas how I can fix this?

Thanks a lot,
Andreas

PS: After some googling, I believe the problem is that I am running a
version of dpkg that is too old (1.15.5.6, but I would need >1.15.6, I
think). Anyway, any workaround to make apt-get work again, incl. support
for data.tar.xz, is highly appreciated!