Index: gcc/gcc/config/i386/mingw32.h
===================================================================
--- gcc.orig/gcc/config/i386/mingw32.h  2010-07-20 19:52:41.000000000 +0200
+++ gcc/gcc/config/i386/mingw32.h       2010-08-07 11:45:40.152187500 +0200
@@ -42,7 +42,7 @@
        {                                                       \
          builtin_define ("__MINGW64__");                       \
          builtin_define_std ("WIN64");                         \
-         builtin_define_std ("_WIN64");                        \
+         builtin_define ("_WIN64");                            \
        }                                                       \
     }                                                          \
   while (0)