diff --git a/include/mlang.idl b/include/mlang.idl
index 90eab725cf2..b06e30f5271 100644
--- a/include/mlang.idl
+++ b/include/mlang.idl
@@ -21,7 +21,7 @@ import "unknwn.idl";
 interface IStream;
 
 /* FIXME: LANDID is defined in winnt.h and mlang.h in the platform SDK */
-cpp_quote("#ifndef __WINE_WINNT_H")
+cpp_quote("#ifndef _WINNT_")
 typedef WORD LANGID;
 cpp_quote("#endif")
 
diff --git a/include/winnt.h b/include/winnt.h
index 075e4efcb4b..1dbe3affc06 100644
--- a/include/winnt.h
+++ b/include/winnt.h
@@ -18,8 +18,8 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
-#ifndef __WINE_WINNT_H
-#define __WINE_WINNT_H
+#ifndef _WINNT_
+#define _WINNT_
 
 #include <basetsd.h>
 
@@ -3648,4 +3648,4 @@ ULONGLONG WINAPI VerSetConditionMask(ULONGLONG,DWORD,BYTE);
 #define	VER_AND					6
 #define	VER_OR					7
 
-#endif  /* __WINE_WINNT_H */
+#endif  /* _WINNT_ */