# in lib/acts_as_xapian.rb, at line 597:
        # Extract value of a field from the model
        def xapian_value(field, type = nil)
            value = self[field] || self.send(field.to_sym)
            if type == :date
                if value.kind_of?(Time)
                    value.utc.strftime("%Y%m%d")
                elsif value.kind_of?(Date)
                    value.to_time.utc.strftime("%Y%m%d")
                else
                    raise "Only Time or Date types supported by acts_as_xapian for :date fields, got " + value.class.to_s
                end
+           elsif type == :number
+             Xapian::sortable_serialise(value)
            elsif type == :boolean
                value ? true : false
            else
                value.to_s
            end
        end