on Ultrasphinx Associations

I am new to ultrasphinx and I am struggling with this issue.

I ve got a model with the following associations and is_indexed options:

class Item has_many :keywords

is_indexed :fields => ['id', 'collection_id','subject_area', 'special_interest', 'notes', 'abstract'], :concatenate => [{:association_name => 'keywords', :field => 'keyword', :as => 'keyword_text'}] end

When I try this in the console:

@b=Ultrasphinx::Search.new(:query => "Immoral behavior").run.results

I get 5 objects back, they do so because I know they match one of the keywords in the :keywords assocations

[#<Item id: 329, collection_id: 117, notes: "", size_scope: "25 items", special_interest: "", subject_area: "WIH", abstract: "While Evaline (Eva) Foster was in Malaysia from 189...">, #<Item id: 308, collection_id: 137, notes: "This letter originated special_interest: "", subject_area: "WIH", abstract: "While his wife, Clara Jones Crittenden, stayed with...">, #<Item id: 1214, collection_id: 110, notes: "", size_scope: "35 letters (approximately)", special_interest: "", subject_area: "A-A", abstract: "Of the Fenno-Hoffman Family papers, the letters wri...">, #<Item id: 271, collection_id: 319, notes: "M-3462.2", size_scope: "1 page", special_interest: "", subject_area: "WIH", abstract: "Joseph F. Huntoon wrote this letter to his wife, Be...">, #<Item id: 1207, collection_id: 2, notes: "", size_scope: "3 pages", special_interest: "", subject_area: "A-A", abstract: "Letter from Oliver Swaine Taylor to an unidentified...">]

The problem is that in the fields retrieved in each object I don't see the one I specified in the : concatenate options named 'keyword_text' which is the one causing the matching.

Any help on how I can have access to those fields?

thanks! s.