That works!
      
      
      
      I tried it with jessie-backports as well, and I got:
      
      
      
      root@kmac:~# apt update
      
      Ign http://archive.debian.org jessie InRelease
      
      Get:1 http://archive.debian.org jessie-backports
            InRelease [166 kB]
      
      W: There is no public
            key available for the following key IDs:
      
      8B48AD6246925553
      
      E: Release file for http://archive.debian.org/debian/dists/jessie-backports/InRelease is expired (invalid
            since 424d 14h 54min 36s). Updates for this repository will
            not be applied.
      
      
      
      Any
          clues as to how to deal with that?