Weird YAML delegator bug

output.bash

jeff ~/Workspace/test $ cat test.rb 
require 'delegate'
require 'yaml'

class A < DelegateClass(Array)
  def initialize(*args)
    super(Array.new(*args))
  end
end

p YAML.dump(A.new)
jeff ~/Workspace/test $ ruby -v
ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin10.8.0]
jeff ~/Workspace/test $ ruby test.rb 
/Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:25:in `block in initialize': undefined method `name' for nil:NilClass (NoMethodError)
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `yield'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `default'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `block in initialize'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `yield'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `default'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `block in initialize'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `yield'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `default'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `block in initialize'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `yield'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `default'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `block in initialize'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:102:in `yield'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:102:in `default'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:102:in `accept'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:66:in `push'
	from /Users/jeff/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/psych.rb:189:in `dump'
	from test.rb:10:in `<main>'
jeff ~/Workspace/test $ rvm use 1.9.2
Using /Users/jeff/.rvm/gems/ruby-1.9.2-p290
jeff ~/Workspace/test $ ruby test.rb 
"--- []\n\n"
jeff ~/Workspace/test $ bundle exec ruby test.rb 
/Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:20:in `block in initialize': undefined method `name' for nil:NilClass (NoMethodError)
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in `yield'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in `default'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in `block in initialize'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in `yield'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in `default'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in `block in initialize'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in `yield'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in `default'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in `block in initialize'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in `yield'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in `default'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in `block in initialize'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:63:in `yield'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:63:in `default'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:63:in `accept'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:36:in `<<'
	from /Users/jeff/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/psych.rb:165:in `dump'
	from test.rb:10:in `<main>'