public_method_defined? on a metaclass doesn't work

[eloy.de.enige@…]

% cat t.rb
class X
  def self.metaclass
    class << self; self; end
  end
  
  class << self
    def public_method; end
  end
end

p X.metaclass.public_method_defined?(:public_method)

% ruby19 t.rb
true

% macruby t.rb
false

[watson1978@…]

It seems to work well ;) I checked with r5180.