Ferret::Index::Index#scan

Hi everyone, I’m having trouble with the Index scan() method. When I
call it, I receive a ‘private method called’ error. Example:

index.scan(‘blah’)
→ private method `scan’ called for #Ferret::Index::Index:0xb7c15374
(NoMethodError)

I tried it on the searcher as well:

index.searcher.scan(‘blah’)
→ private method `scan’ called for #<Ferret::Search::Searcher:
0xb7c0161c> (NoMethodError)

scan() docs:
http://ferret.davebalmain.com/api/classes/Ferret/Index/Index.html#M000024

I’m using ferret-0.11.6.

Can anyone offer any suggestions?

Thanks,

Derek