Sequel error in macruby

gistfile1.rb

require 'rubygems'
require 'sequel'

DB = Sequel.sqlite

DB.create_table :models do
  primary_key :id
  
  column :first_attr,  :fixnum
  column :second_attr, :string
end

class Model < Sequel::Model
end

# filtering with two conditions
Model.filter(:first_attr => 1, :second_attr => 'foo').first