gpg-agent: use --disable-scdaemon, yet still get SC-related error?

[Jim Meyering]

Does this ring a bell with anyone?

I'm using gpg-agent from Fedora 16's gnupg2-2.0.18-2.fc16.x86_64,
invoked with these options:

    exec gpg-agent --daemon \
        --disable-scdaemon \
        --enable-ssh-support \
        --use-standard-socket \
        --log-file $HOME/.ssh/log \
      $HOME/.xinitrc-real

Yet in spite of that --disable-scdaemon option, I still get what looks
like an SC-related error in the log each time I try to use gpg:
(and the agent fails to do its job):

    2011-11-27 22:29:21 gpg-agent[13380] error getting default authentication
      keyID of card: Not supported