Error using carrierwave on image processing

Error using carrierwave on image processing

I keep getting this error when uploading a file using carrierwave.
undefined method `process' for
/uploads/tmp/1377378142-19197-6422/4.jpg:AvatarUploader
I am trying to resize an image on upload, I have minimagick installed.
This is what the avater uploader looks like:
# Process files as they are uploaded:
process :scale => [200, 300]
#
def scale(width, height)
process resize_to_fill: [200, 300]
end
Any ideas what could be wrong ? I am using rails 4.0