diff --git a/lib/rdoc.rb b/lib/rdoc.rb
index 043d342..b3d15e9 100644
--- a/lib/rdoc.rb
+++ b/lib/rdoc.rb
@@ -391,5 +391,15 @@ module RDoc
   METHOD_MODIFIERS = GENERAL_MODIFIERS +
     %w[arg args yield yields notnew not-new not_new doc]
 
+  def self.yamler # :nodoc:
+    @yamler ||=
+      begin
+        require 'psych'
+        Psych
+      rescue LoadError
+        require 'yaml'
+        YAML
+      end
+  end
 end
 
diff --git a/lib/rdoc/ri/descriptions.rb b/lib/rdoc/ri/descriptions.rb
index 467b7de..529dee6 100644
--- a/lib/rdoc/ri/descriptions.rb
+++ b/lib/rdoc/ri/descriptions.rb
@@ -1,4 +1,9 @@
-require 'yaml'
+begin
+  require 'psych'
+rescue LoadError
+  require 'yaml'
+end
+
 require 'rdoc/markup/fragments'
 require 'rdoc/ri'
 
@@ -66,7 +71,7 @@ class RDoc::RI::Description
   end
 
   def self.deserialize(from)
-    YAML.load(from)
+    RDoc.yamler.load(from)
   end
 
   def <=>(other)
diff --git a/lib/rdoc/ri/driver.rb b/lib/rdoc/ri/driver.rb
index 89534a5..e134e5e 100644
--- a/lib/rdoc/ri/driver.rb
+++ b/lib/rdoc/ri/driver.rb
@@ -1,5 +1,4 @@
 require 'optparse'
-require 'yaml'
 
 require 'rdoc/ri'
 require 'rdoc/ri/paths'
diff --git a/lib/rubygems.rb b/lib/rubygems.rb
index 95cdee8..a5e1b05 100644
--- a/lib/rubygems.rb
+++ b/lib/rubygems.rb
@@ -988,6 +988,16 @@ module Gem
 
   YAML_SPEC_DIR = 'quick/'
 
+  def self.yamler # :nodoc:
+    @yamler ||=
+      begin
+        require 'psych'
+        Psych
+      rescue LoadError
+        require 'yaml'
+        YAML
+      end
+  end
 end
 
 module Kernel
diff --git a/lib/rubygems/builder.rb b/lib/rubygems/builder.rb
index 9e7f262..ff0fe0c 100644
--- a/lib/rubygems/builder.rb
+++ b/lib/rubygems/builder.rb
@@ -18,7 +18,6 @@ class Gem::Builder
   # spec:: [Gem::Specification] The specification instance
 
   def initialize(spec)
-    require "yaml"
     require "rubygems/package"
     require "rubygems/security"
 
@@ -70,7 +69,7 @@ EOM
   def write_package
     open @spec.file_name, 'wb' do |gem_io|
       Gem::Package.open gem_io, 'w', @signer do |pkg|
-        pkg.metadata = @spec.to_yaml
+        pkg.metadata = Gem.yamler.dump @spec
 
         @spec.files.each do |file|
           next if File.directory? file
diff --git a/lib/rubygems/commands/mirror_command.rb b/lib/rubygems/commands/mirror_command.rb
index 7cb8583..2658777 100644
--- a/lib/rubygems/commands/mirror_command.rb
+++ b/lib/rubygems/commands/mirror_command.rb
@@ -1,4 +1,3 @@
-require 'yaml'
 require 'zlib'
 
 require 'rubygems/command'
@@ -29,7 +28,7 @@ Multiple sources and destinations may be specified.
 
     raise "Config file #{config_file} not found" unless File.exist? config_file
 
-    mirrors = YAML.load_file config_file
+    mirrors = Gem.yamler.load_file config_file
 
     raise "Invalid config file #{config_file}" unless mirrors.respond_to? :each
 
diff --git a/lib/rubygems/commands/owner_command.rb b/lib/rubygems/commands/owner_command.rb
index e88734e..5ca0152 100644
--- a/lib/rubygems/commands/owner_command.rb
+++ b/lib/rubygems/commands/owner_command.rb
@@ -43,7 +43,7 @@ class Gem::Commands::OwnerCommand < Gem::Command
     end
 
     with_response response do |resp|
-      owners = YAML.load resp.body
+      owners = Gem.yamler.load resp.body
 
       say "Owners for gem: #{name}"
       owners.each do |owner|
diff --git a/lib/rubygems/commands/specification_command.rb b/lib/rubygems/commands/specification_command.rb
index 07d2c2c..9c8eba8 100644
--- a/lib/rubygems/commands/specification_command.rb
+++ b/lib/rubygems/commands/specification_command.rb
@@ -1,4 +1,3 @@
-require 'yaml'
 require 'rubygems/command'
 require 'rubygems/local_remote_options'
 require 'rubygems/version_option'
@@ -106,7 +105,7 @@ FIELD         name of gemspec field to show
       say case options[:format]
           when :ruby then s.to_ruby
           when :marshal then Marshal.dump s
-          else s.to_yaml
+          else Gem.yamler.dump s
           end
 
       say "\n"
diff --git a/lib/rubygems/config_file.rb b/lib/rubygems/config_file.rb
index 3498d06..eed744e 100644
--- a/lib/rubygems/config_file.rb
+++ b/lib/rubygems/config_file.rb
@@ -199,10 +199,8 @@ class Gem::ConfigFile
     dirname = File.dirname(credentials_path)
     Dir.mkdir(dirname) unless File.exists?(dirname)
 
-    require 'yaml'
-
     File.open(credentials_path, 'w') do |f|
-      f.write config.to_yaml
+      f.write Gem.yamler.dump config
     end
 
     @rubygems_api_key = api_key
@@ -211,8 +209,7 @@ class Gem::ConfigFile
   def load_file(filename)
     return {} unless filename and File.exists?(filename)
     begin
-      require 'yaml'
-      YAML.load(File.read(filename))
+      Gem.yamler.load(File.read(filename))
     rescue ArgumentError
       warn "Failed to load #{config_file_name}"
     rescue Errno::EACCES
@@ -301,12 +298,11 @@ class Gem::ConfigFile
       yaml_hash[key.to_s] = value
     end
 
-    yaml_hash.to_yaml
+    Gem.yamler.dump yaml_hash
   end
 
   # Writes out this config file, replacing its source.
   def write
-    require 'yaml'
     open config_file_name, 'w' do |io|
       io.write to_yaml
     end
diff --git a/lib/rubygems/indexer.rb b/lib/rubygems/indexer.rb
index baa5824..a48e34e 100644
--- a/lib/rubygems/indexer.rb
+++ b/lib/rubygems/indexer.rb
@@ -145,7 +145,7 @@ class Gem::Indexer
         spec_file_name = "#{original_name}.gemspec.rz"
         yaml_name = File.join @quick_dir, spec_file_name
 
-        yaml_zipped = Gem.deflate spec.to_yaml
+        yaml_zipped = Gem.deflate Gem.yamler.dump spec
         open yaml_name, 'wb' do |io| io.write yaml_zipped end
 
         progress.updated original_name
@@ -191,7 +191,7 @@ class Gem::Indexer
 
         gems = index.sort_by { |name, gemspec| gemspec.sort_obj }
         gems.each do |original_name, gemspec|
-          yaml = gemspec.to_yaml.gsub(/^/, '    ')
+          yaml = Gem.yamler.dump(gemspec).gsub(/^/, '    ')
           yaml = yaml.sub(/\A    ---/, '') # there's a needed extra ' ' here
           io.print "  #{original_name}:"
           io.puts yaml
diff --git a/lib/rubygems/old_format.rb b/lib/rubygems/old_format.rb
index 43967db..c3b7226 100644
--- a/lib/rubygems/old_format.rb
+++ b/lib/rubygems/old_format.rb
@@ -6,7 +6,6 @@
 
 require 'rubygems'
 require 'fileutils'
-require 'yaml'
 require 'zlib'
 
 ##
@@ -133,7 +132,7 @@ class Gem::OldFormat
       self.read_until_dashes(gem_file) do |line|
         header_yaml << line
       end
-      header = YAML.load(header_yaml)
+      header = Gem.yamler.load(header_yaml)
       raise Gem::Exception, errstr unless header
 
       header.each do |entry|
diff --git a/lib/rubygems/package.rb b/lib/rubygems/package.rb
index 0fd6402..c73e7ae 100644
--- a/lib/rubygems/package.rb
+++ b/lib/rubygems/package.rb
@@ -7,7 +7,6 @@
 require 'fileutils'
 require 'find'
 require 'stringio'
-require 'yaml'
 require 'zlib'
 
 require 'rubygems/security'
diff --git a/lib/rubygems/server.rb b/lib/rubygems/server.rb
index 24c9e04..1800a27 100644
--- a/lib/rubygems/server.rb
+++ b/lib/rubygems/server.rb
@@ -1,5 +1,4 @@
 require 'webrick'
-require 'yaml'
 require 'zlib'
 require 'erb'
 
@@ -577,7 +576,7 @@ div.method-source-code pre { color: #ffdead; overflow: hidden; }
         res.body << Gem.deflate(Marshal.dump(specs.first))
       else # deprecated YAML format
         res['content-type'] = 'application/x-deflate'
-        res.body << Gem.deflate(specs.first.to_yaml)
+        res.body << Gem.deflate(Gem.yamler.dump(specs.first))
       end
     else
       raise WEBrick::HTTPStatus::NotFound, "`#{req.path}' not found."
@@ -823,7 +822,7 @@ div.method-source-code pre { color: #ffdead; overflow: hidden; }
 
     res['date'] = File.stat(@spec_dir).mtime
 
-    index = @source_index.to_yaml
+    index = Gem.yamler.dump @source_index
 
     if req.path =~ /Z$/ then
       res['content-type'] = 'application/x-deflate'
diff --git a/lib/rubygems/source_index.rb b/lib/rubygems/source_index.rb
index ac5d8ad..b44f3ca 100644
--- a/lib/rubygems/source_index.rb
+++ b/lib/rubygems/source_index.rb
@@ -449,7 +449,7 @@ class Gem::SourceIndex
         if name =~ /Marshal/ then
           return Marshal.load(spec_data)
         else
-          return YAML.load(spec_data)
+          return Gem.yamler.load(spec_data)
         end
       rescue => e
         if Gem.configuration.really_verbose then
@@ -549,7 +549,7 @@ class Gem::SourceIndex
     begin
       yaml_uri = source_uri + "quick/#{spec_name}.gemspec.rz"
       zipped = fetcher.fetch_path yaml_uri
-      return YAML.load(unzip(zipped))
+      return Gem.yamler.load(unzip(zipped))
     rescue => ex
       @fetch_error = ex
       if Gem.configuration.really_verbose then
diff --git a/lib/rubygems/specification.rb b/lib/rubygems/specification.rb
index 472d608..31ef356 100644
--- a/lib/rubygems/specification.rb
+++ b/lib/rubygems/specification.rb
@@ -477,7 +477,7 @@ class Gem::Specification
 
   def self.from_yaml(input)
     input = normalize_yaml_input input
-    spec = YAML.load input
+    spec = Gem.yamler.load input
 
     if spec && spec.class == FalseClass then
       raise Gem::EndOfYAMLException
@@ -677,33 +677,44 @@ class Gem::Specification
     }
   end
 
-  def to_yaml(opts = {}) # :nodoc:
+  def encode_with coder # :nodoc:
     mark_version
 
     attributes = @@attributes.map { |name,| name.to_s }.sort
     attributes = attributes - %w[name version platform]
 
-    yaml = YAML.quick_emit object_id, opts do |out|
-      out.map taguri, to_yaml_style do |map|
-        map.add 'name', @name
-        map.add 'version', @version
-        platform = case @original_platform
-                   when nil, '' then
-                     'ruby'
-                   when String then
-                     @original_platform
-                   else
-                     @original_platform.to_s
-                   end
-        map.add 'platform', platform
+    coder.add 'name', @name
+    coder.add 'version', @version
 
-        attributes.each do |name|
-          map.add name, instance_variable_get("@#{name}")
-        end
+    platform = case @original_platform
+               when nil, '' then
+                 'ruby'
+               when String then
+                 @original_platform
+               else
+                 @original_platform.to_s
+               end
+    coder.add 'platform', platform
+
+    attributes.each do |name|
+      coder.add name, instance_variable_get("@#{name}")
+    end
+  end
+
+  def to_yaml(opts = {}) # :nodoc:
+    return super unless 'YAML' == Gem.yamler.name
+
+    yaml = Gem.yamler.quick_emit object_id, opts do |out|
+      out.map taguri, to_yaml_style do |map|
+        encode_with map
       end
     end
   end
 
+  def init_with coder # :nodoc:
+    yaml_initialize coder.tag, coder.map
+  end
+
   def yaml_initialize(tag, vals) # :nodoc:
     vals.each do |ivar, val|
       instance_variable_set "@#{ivar}", val
diff --git a/test/rubygems/gemutilities.rb b/test/rubygems/gemutilities.rb
index 965d898..e9d876f 100644
--- a/test/rubygems/gemutilities.rb
+++ b/test/rubygems/gemutilities.rb
@@ -8,19 +8,12 @@ else
   require 'rubygems'
 end
 require 'fileutils'
-begin
-  gem 'minitest', '>= 1.3.1'
-  require 'minitest/unit'
-rescue Gem::LoadError
-  warn "Install minitest gem >= 1.3.1"
-  raise
-end
+require 'minitest/autorun'
 require 'tmpdir'
 require 'uri'
 require 'rubygems/package'
 require 'rubygems/test_utilities'
 require 'pp'
-require 'yaml'
 
 begin
   gem 'rdoc'
@@ -137,25 +130,9 @@ class RubyGemTestCase < MiniTest::Unit::TestCase
     Gem.pre_uninstall do |uninstaller|
       @pre_uninstall_hook_arg = uninstaller
     end
-
-    Object.class_eval %q{
-      alias tmp_to_yaml to_yaml
-      def to_yaml( opts = {} )
-        YAML::quick_emit( self, opts ) do |out|
-          out.map( taguri, to_yaml_style ) do |map|
-            to_yaml_properties.each do |m|
-              map.add( m[1..-1], instance_variable_get( m ) )
-            end
-          end
-        end
-      end
-    }
   end
 
   def teardown
-    Object.class_eval %q{
-      alias to_yaml tmp_to_yaml
-    }
     Gem::ConfigMap[:BASERUBY] = @orig_BASERUBY
     Gem::ConfigMap[:arch] = @orig_arch
 
diff --git a/test/rubygems/test_gem_commands_specification_command.rb b/test/rubygems/test_gem_commands_specification_command.rb
index 6a43439..4e4988b 100644
--- a/test/rubygems/test_gem_commands_specification_command.rb
+++ b/test/rubygems/test_gem_commands_specification_command.rb
@@ -80,7 +80,7 @@ class TestGemCommandsSpecificationCommand < RubyGemTestCase
       @cmd.execute
     end
 
-    assert_equal "foo", YAML.load(@ui.output)
+    assert_equal "foo", Gem.yamler.load(@ui.output)
   end
 
   def test_execute_marshal
diff --git a/test/rubygems/test_gem_gemcutter_utilities.rb b/test/rubygems/test_gem_gemcutter_utilities.rb
index f8306d5..ec10698 100644
--- a/test/rubygems/test_gem_gemcutter_utilities.rb
+++ b/test/rubygems/test_gem_gemcutter_utilities.rb
@@ -22,7 +22,7 @@ class TestGemGemcutterUtilities < RubyGemTestCase
     assert @fetcher.last_request["authorization"]
     assert_match %r{Signed in.}, @sign_in_ui.output
 
-    credentials = YAML.load_file Gem.configuration.credentials_path
+    credentials = Gem.yamler.load_file Gem.configuration.credentials_path
     assert_equal api_key, credentials[:rubygems_api_key]
   end
 
@@ -34,7 +34,7 @@ class TestGemGemcutterUtilities < RubyGemTestCase
     assert @fetcher.last_request["authorization"]
     assert_match %r{Signed in.}, @sign_in_ui.output
 
-    credentials = YAML.load_file Gem.configuration.credentials_path
+    credentials = Gem.yamler.load_file Gem.configuration.credentials_path
     assert_equal api_key, credentials[:rubygems_api_key]
   end
 
@@ -60,7 +60,7 @@ class TestGemGemcutterUtilities < RubyGemTestCase
     assert_match %r{Enter your RubyGems.org credentials.}, @sign_in_ui.output
     assert_match %r{Signed in.}, @sign_in_ui.output
 
-    credentials   = YAML.load_file Gem.configuration.credentials_path
+    credentials   = Gem.yamler.load_file Gem.configuration.credentials_path
     assert_equal api_key, credentials[:rubygems_api_key]
     assert_equal other_api_key, credentials[:other_api_key]
   end
diff --git a/test/rubygems/test_gem_indexer.rb b/test/rubygems/test_gem_indexer.rb
index 7bc4862..8ae187a 100644
--- a/test/rubygems/test_gem_indexer.rb
+++ b/test/rubygems/test_gem_indexer.rb
@@ -521,7 +521,7 @@ eighty characters.&lt;/pre&gt;
     yaml_path = File.join @tempdir, 'yaml'
     dump_path = File.join @tempdir, "Marshal.#{@marshal_version}"
 
-    yaml_index = YAML.load_file yaml_path
+    yaml_index = Gem.yamler.load_file yaml_path
     dump_index = Marshal.load Gem.read_binary(dump_path)
 
     dump_index.each do |_,gem|
diff --git a/test/rubygems/test_gem_server.rb b/test/rubygems/test_gem_server.rb
index 41c25fe..dbb53e3 100644
--- a/test/rubygems/test_gem_server.rb
+++ b/test/rubygems/test_gem_server.rb
@@ -108,7 +108,7 @@ class TestGemServer < RubyGemTestCase
     assert @res['date']
     assert_equal 'application/x-deflate', @res['content-type']
 
-    spec = YAML.load Gem.inflate(@res.body)
+    spec = Gem.yamler.load Gem.inflate(@res.body)
     assert_equal 'a', spec.name
     assert_equal Gem::Version.new(1), spec.version
   end
@@ -125,7 +125,7 @@ class TestGemServer < RubyGemTestCase
     assert @res['date']
     assert_equal 'application/x-deflate', @res['content-type']
 
-    spec = YAML.load Gem.inflate(@res.body)
+    spec = Gem.yamler.load Gem.inflate(@res.body)
     assert_equal 'a', spec.name
     assert_equal Gem::Version.new(1), spec.version
     assert_equal Gem::Platform.local, spec.platform
@@ -143,7 +143,7 @@ class TestGemServer < RubyGemTestCase
     assert @res['date']
     assert_equal 'application/x-deflate', @res['content-type']
 
-    spec = YAML.load Gem.inflate(@res.body)
+    spec = Gem.yamler.load Gem.inflate(@res.body)
     assert_equal 'a', spec.name
     assert_equal Gem::Version.new(1), spec.version
   end
@@ -307,7 +307,7 @@ class TestGemServer < RubyGemTestCase
     si = Gem::SourceIndex.new
     si.add_specs @a1, @a2
 
-    assert_equal si, YAML.load(@res.body)
+    assert_equal si, Gem.yamler.load(@res.body)
   end
 
   def test_yaml_Z
@@ -323,7 +323,7 @@ class TestGemServer < RubyGemTestCase
     si = Gem::SourceIndex.new
     si.add_specs @a1, @a2
 
-    assert_equal si, YAML.load(Gem.inflate(@res.body))
+    assert_equal si, Gem.yamler.load(Gem.inflate(@res.body))
   end
 
   def util_listen
diff --git a/test/rubygems/test_gem_specification.rb b/test/rubygems/test_gem_specification.rb
index 5979890..0718149 100644
--- a/test/rubygems/test_gem_specification.rb
+++ b/test/rubygems/test_gem_specification.rb
@@ -1,6 +1,7 @@
 require_relative 'gemutilities'
 require 'stringio'
 require 'rubygems/specification'
+require 'date'
 
 class TestGemSpecification < RubyGemTestCase
 
@@ -855,7 +856,7 @@ end
 
   def test_to_yaml
     yaml_str = @a1.to_yaml
-    same_spec = YAML.load(yaml_str)
+    same_spec = Gem.yamler.load(yaml_str)
 
     assert_equal @a1, same_spec
   end
@@ -864,7 +865,7 @@ end
     @a1.platform = Gem::Platform.local
     yaml_str = @a1.to_yaml
 
-    same_spec = YAML.load(yaml_str)
+    same_spec = Gem.yamler.load(yaml_str)
 
     assert_equal Gem::Platform.local, same_spec.platform
 
@@ -883,7 +884,7 @@ end
 
     yaml_str = @a1.to_yaml
 
-    same_spec = YAML.load(yaml_str)
+    same_spec = Gem.yamler.load(yaml_str)
 
     assert_equal Gem::Platform.new('powerpc-darwin7'), same_spec.platform
     assert_equal 'powerpc-darwin7.9.0', same_spec.original_platform