Index: test/test_gem_platform.rb
===================================================================
--- test/test_gem_platform.rb	(revision 1414)
+++ test/test_gem_platform.rb	(working copy)
@@ -51,6 +51,7 @@ class TestGemPlatform < RubyGemTestCase
       'i386-linux-gnu'         => ['x86',       'linux',     nil],
       'i386-mingw32'           => ['x86',       'mingw32',   nil],
       'i386-mswin32'           => ['x86',       'mswin32',   nil],
+      'i386-mswin32_80'        => ['x86',       'mswin32',   '80'],
       'i386-netbsdelf'         => ['x86',       'netbsdelf', nil],
       'i386-openbsd4.0'        => ['x86',       'openbsd',   '4.0'],
       'i386-solaris2.10'       => ['x86',       'solaris',   '2.10'],
@@ -66,6 +67,21 @@ class TestGemPlatform < RubyGemTestCase
     end
   end
 
+  def test_initialize_mswin32_vc6
+    orig_RUBY_SO_NAME = Config::CONFIG['RUBY_SO_NAME']
+    Config::CONFIG['RUBY_SO_NAME'] = 'msvcrt-ruby18'
+
+    util_set_arch 'i386-mswin32'
+
+    expected = %w[x86 mswin32 60]
+
+    platform = Gem::Platform.new('i386-mswin32')
+
+    assert_equal expected, platform.to_a, 'i386-mswin32 VC6'
+  ensure
+    Config::CONFIG['RUBY_SO_NAME'] = orig_RUBY_SO_NAME
+  end
+
   def test_initialize_test
     platform = Gem::Platform.new 'cpu-my_platform1'
     assert_equal 'cpu', platform.cpu
Index: lib/rubygems/platform.rb
===================================================================
--- lib/rubygems/platform.rb	(revision 1414)
+++ lib/rubygems/platform.rb	(working copy)
@@ -46,7 +46,14 @@ class Gem::Platform
                       when /^java([\d.]*)/ then        [ 'java',      $1  ]
                       when /linux/ then                [ 'linux',     $1  ]
                       when /mingw32/ then              [ 'mingw32',   nil ]
-                      when /mswin32/ then              [ 'mswin32',   nil ]
+                      when /mswin32(\_(\d+))?/ then
+                        if $2 then
+                          [ 'mswin32', $2   ]
+                        elsif Config::CONFIG['RUBY_SO_NAME'] =~ /^msvcrt-ruby/ then
+                          [ 'mswin32', '60' ]
+                        else
+                          [ 'mswin32', nil  ]
+                        end
                       when /netbsdelf/ then            [ 'netbsdelf', nil ]
                       when /openbsd(\d+\.\d+)/ then    [ 'openbsd',   $1  ]
                       when /solaris(\d+\.\d+)/ then    [ 'solaris',   $1  ]
@@ -98,7 +105,7 @@ class Gem::Platform
               when /^i686-darwin(\d)/ then     ['x86',       'darwin',  $1]
               when /^i\d86-linux/ then         ['x86',       'linux',   nil]
               when 'java', 'jruby' then        [nil,         'java',    nil]
-              when /mswin32/ then              ['x86',       'mswin32', nil]
+              when /mswin32(\_(\d+))?/ then    ['x86',       'mswin32', $2]
               when 'powerpc-darwin' then       ['powerpc',   'darwin',  nil]
               when /powerpc-darwin(\d)/ then   ['powerpc',   'darwin',  $1]
               when /sparc-solaris2.8/ then     ['sparc',     'solaris', '2.8']