Ruby 2.0's refinements aren't so refined... yet?

I began fiddling with the cool new features in Ruby 2.0.0-rc2 and quickly ran into some strangeness:

# refine_test.rb
module Doubler
  refine Fixnum do
    def double
      self * 2
    end
  end
end

using Doubler
class Thing
  def initialize
    p 2.double
  end
end

# using Doubler #=> putting this here would result in
# line 10 producing a NoMethodError for `2.double`
Thing.new  # => 4
p 2.double  # => 4
load 'refine_load_file_test.rb'

And the other file:

# refine_load_file_test.rb
Thing.new  # => 4
p 2.double  # => NoMethodError

The load command runs Thing.new and returns a 4 just peachy… however the next line fails. Ruby-doc doesn’t give any clues as to why this would work like that.