Binarylogic Searchlogic

I'm currently trying Searchlogic but have find to have some issues making it work properly.

After installing it (either by using gem or plugin) it get this error when starting my server:

/Users/alvaropereyrarabanal/Development/SK/vendor/plugins/binarylogic-searchlogic/lib/
searchlogic/conditions/magic_methods.rb:8:in `included': undefined method `metaclass' for 
Searchlogic::Conditions::Base:Class (NoMethodError)

which mentions this line:

      def self.included(klass)
        klass.metaclass.class_eval do
          include ClassMethods
          attr_accessor :added_column_equals_conditions, :added_associations
        end

I tried changing the line to

      def self.included(klass)
        klass.class_eval do
          include ClassMethods
          attr_accessor :added_column_equals_conditions, :added_associations
        end

and that seemed to at least let me run. However, when trying to search something with it, it can't find the added_associations from my product model (which is obviously something that must be added on the line I modified):

NoMethodError (undefined method `added_associations' for Searchlogic::Cache::ProductConditions:Class):

Is there something wrong I'm doing when trying to start Searchlogic?