[Secure-testing-team] Repository does not work with APT::Default-Release "testing"

[Peter Eisentraut]

I have

APT::Default-Release "testing";

in /etc/apt/apt.conf so that I can safely run a mixed testing/unstable system.
In /etc/apt/sources.list I have

deb     ftp://ftp.de.debian.org/debian/ testing main contrib non-free
deb     http://secure-testing.debian.net/debian-secure-testing testing/security-updates main contrib non-free

With this setting, the secure-testing packages are ignored.  If I remove the
setting in apt.conf, apt-get will pick up the secure-testing packages.

I'm not sure if that is an oversight in the way the secure-testing archive
is built, or can you perhaps suggest a different way to run a
testing+unstable+secure-testing system?