Validation always fails with "Address must be an Integer" ?

example.rb

class Example
  include DataMapper::Resource
  
  property :id, Serial
  property :ip_address, IPAddressInteger
end

example = Example.new
example.ip_address = "10.48.1.1"

example.valid?
# => false

Example.properties[:ip_address].valid?(example.ip_address)
# => true

example.save
# => false

ip_address_integer.rb

require 'ipaddr'

module DataMapper
  class Property
    class IPAddressInteger < Integer
      def initialize(name, model, options = {})
        super
        @format = if options[:version] == :ipv6
          Socket::AF_INET6
        else
          Socket::AF_INET
        end
      end
      
      def primitive?(value)
        value.kind_of?(::String)
      end
      
      def valid?(value, negated = false)
        dump(value).kind_of?(::Integer)
      end
      
      def load(value)
        if value.kind_of?(::Integer)
          IPAddr.new(value, @format).to_s
        else
          value
        end
      end
      
      def dump(value)
        case value
          when ::String   then IPAddr.new(value, @format).to_i
          when ::Integer  then value
        end
      end
    end
  end
end