set :user being ignored?

My local username and my remote username are not the same. I need to
get Capistrano to use the remote username when ssh-ing to the remote
host, but nothing I've tried works. I've tried adding 'set :user,
"remote_user"' in my deploy.rb file as well as my Capfile, and I've
done the same with 'ssh_options[:username] = "remote_user"', as well
as a few other settings I found around the web. None of them have any
effect. No matter what I do, when I run "cap deploy" Capistrano tries
to ssh to the remote host using my local username.

What's the secret handshake?

Thanks,
-Bill