--- lib/rdoc/options.rb.orig	2007-10-23 17:36:41.000000000 +0200
+++ lib/rdoc/options.rb	2007-10-23 17:37:12.000000000 +0200
@@ -544,7 +544,7 @@
   # so we'll bypass the test under Windows
 
   def check_diagram
-    return if RUBY_PLATFORM =~ /win/
+    return if RUBY_PLATFORM =~ /mswin32|cygwin|mingw|bccwin/
 
     ok = false
     ver = nil