barcode-generator -matsimitsu - NoMethodError

I'm using Matsimitsu's Barcode Generator:

http://github.com/matsimitsu/barcode-generator

and have installed: gbarcode (0.98.16), rmagick (2.12.2) and have
installed the files to: Vendor/Plugins/ directory and successfully ran
the rake barcode_setup command to create the public/images/barcodes
dir.

I Tried using the sample code: <%= barcode 'FJJ4JD'%> in one of my
html.erb files, with the returned message: