Error when using gchart (googlecharts) gem - NameError: uninitialized constant Gchart

Question

http://googlecharts.rubyforge.org/

I installed it with: sudo gem install googlecharts

It installed fine, but whenever I try to use it I get: NameError: uninitialized constant Gchart

Here is the code I am running:

$ irb
>> require 'gchart'
=> true
>> Gchart.line(:data => [0, 40, 10, 70, 20])
NameError: uninitialized constant Gchart
    from (irb):2