require 'couchbase' fails - LoadError - not found

I can't include/'require' the couchbase gem. Installation was successful and also libcouchbase is installed. There's no further error message.

lightbox: me$ gem install couchbase --pre
Successfully installed couchbase-1.2.0.z.beta
1 gem installed
Installing ri documentation for couchbase-1.2.0.z.beta...
Installing RDoc documentation for couchbase-1.2.0.z.beta...

lightbox: me$ cat test.rb
require 'couchbase'
c = Couchbase.new("http://localhost:8091/pools/default")

lightbox: me$ ruby test.rb
/Users/me/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- couchbase (LoadError)
from /Users/me/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from test.rb:1:in `<main>'

lightbox: me$ rails console
Loading development environment (Rails 3.2.6)
1.9.3p194 :001 > require 'couchbase'
LoadError: cannot load such file -- couchbase
from /Users/me/.rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.2.6/lib/active_support/dependencies.rb:251:in `require'
from /Users/me/.rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.2.6/lib/active_support/dependencies.rb:251:in `block in require'
from /Users/me/.rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.2.6/lib/active_support/dependencies.rb:236:in `load_dependency'
from /Users/me/.rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.2.6/lib/active_support/dependencies.rb:251:in `require'
from (irb):1
from /Users/me/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.6/lib/rails/commands/console.rb:47:in `start'
from /Users/me/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.6/lib/rails/commands/console.rb:8:in `start'
from /Users/me/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.6/lib/rails/commands.rb:41:in `<top (required)>'
from script/rails:9:in `require'
from script/rails:9:in `<main>'
1.9.3p194 :002 >