M-. should bring back last arg of prev cmd

[Nick Croft <nicko@xxxxxxxxxxx>]

Hi. Another question. You help has been much appreciated.

I learnt in an article by Dominic Mitchell "A Case for the Z Shell",
that M-. can be used as a shortcut for the last argument of the previous
command.

  % cat /etc/networks
  % ls -l /etc/hosts
  % vi M-.
  % vi /etc/hosts M-.M-.
  % vi /etc/hosts /etc/networks

Question: Is this dependent on some setting in the .zshrc, or a setopt
command? I had it working a few days ago. I think it's the greatest
thing since sliced bread. 

But it's gone, and I suspect I've overridden whatever it depended on.

Clues, anyone?

Nick