Getting 404 from security.debian.org trying to install a package

[John W <jwdevel@gmail.com>]

I am using Debian 7.4 (wheezy) which I realize is on LTS.

I'm trying to install a package, but I get a 404 error:

    $ sudo aptitude install libmagick++5
    The following NEW packages will be installed:
      libmagick++5
    0 packages upgraded, 1 newly installed, 0 to remove and 315 not upgraded.
    Need to get 237 kB of archives. After unpacking 635 kB will be used.
    Err http://security.debian.org/ wheezy/updates/main libmagick++5
amd64 8:6.7.7.10-5+deb7u6
      404  Not Found [IP: 128.101.240.215 80]
    0% [Working]E: Failed to fetch
http://security.debian.org/pool/updates/main/i/imagemagick/libmagick++5_6.7.7.10-5+deb7u6_amd64.deb:
404  Not Found [IP: 128.101.240.215 80]

If I look at the listing on the site:
http://security.debian.org/pool/updates/main/i/imagemagick/
I see:
    libmagick++5_6.7.7.10-5+deb7u14_amd64.deb

So it looks like the "u14" version is available, but for whatever
reason my install is trying to get "u6" which is no longer there.

Okay, I don't mind using the newer "u14" one... how do I tell aptitude
to use that, though?

Thanks
-John