Rails 4 Sunspot Facets: Undefined method split

[Af Dig]

I am trying to use facets with a job model. This is my code:

Model: Job - searchable

   

searchable do
        text :name, :boost => 5
        text :description
        text :subcategory
        integer :subcategory_id, references: :subcategory
    end

Controller: Index Action

    def index
     if params[:q]
      @search = Job.search do
         keywords params[:q] do
          highlight :name, :description
         end
         with(:subcategory_id)
         facet(:subcategory_id)
      end
       @jobs = @search.results
     else
      @jobs = Job.all.order('created_at desc')
     end


     @job = Job.new
    end

View Index + Search Results Page

   

%ul.facet
      - @search.facet(:subcategory_id).rows.each do |row|
        = link_to row.instance.name, url_for(subcategory_id: row.value)
        = "(#{row.count})"

   

I am now getting an error that says 

"undefined method `split' for :subcategory:Symbol"

Where am I going wrong? Job - searchable