Require problem with payment gem

I did a “gem install payment”, version 1.0.1. The require statement in
my controller:

require 'payment/authorize_net'

…returns a “no file to load” error.

I ended up copying the files from the gem’s lib subfolder to my
application’s lib folder and everything worked from there. Doesn’t seem
right, though.

What am I missing with respect to properly requiring the gem from where
it is installed?

thanks.
c.