gistfile1.txt

#!/usr/bin/env ruby

require 'dm-core'
require 'dm-validations'

class Foo
  include DataMapper::Resource

  property :id, Serial
  property :age_check, Boolean # change this to String and the validation works as expected

  validates_is_accepted :age_check, :allow_nil => false, :message => 'You need to check the age'

end

DataMapper.setup(:default, 'sqlite3::memory:')
DataMapper.auto_migrate!

p Foo.new(:age_check => false).valid? # true, should be false