Iceweasel 36bpo70+1 signing error

[gwillems]

When trying to update Iceweasel i get an unsigned error.

apt-key --keyring /etc/apt/trusted.gpg.d/pkg-mozilla-archive-keyring.gpg 
finger
/etc/apt/trusted.gpg.d/pkg-mozilla-archive-keyring.gpg
------------------------------------------------------
pub   4096R/06C4AE2A 2010-11-20 [expires: 2019-11-13]
       Key fingerprint = 85F0 6FBC 75E0 67C3 F305  C3C9 85A3 D265 06C4 AE2A
uid                  Debian Mozilla team APT archive 
<pkg-mozilla-maintainers at lists.alioth.debian.org>


apt-cache policy iceweasel
iceweasel:
   Installed: 35.0.1-1~bpo70+1
   Candidate: 36.0-1~bpo70+1
   Version table:
      36.0-1~bpo70+1 0
         500 http://mozilla.debian.net/ 
wheezy-backports/iceweasel-release amd64 Packages
  *** 35.0.1-1~bpo70+1 0
         100 /var/lib/dpkg/status
      31.5.0esr-1~deb7u1 0
         500 http://security.debian.org/ wheezy/updates/main amd64 Packages
      31.3.0esr-1~deb7u1 0
         500 http://ftp.uk.debian.org/debian/ wheezy/main amd64 Packages


Gerard Willems,
Netherlands.