diff --git a/winsup/w32api/ChangeLog b/winsup/w32api/ChangeLog
index d539e6f3e..6c319f721 100644
--- a/winsup/w32api/ChangeLog
+++ b/winsup/w32api/ChangeLog
@@ -1,3 +1,8 @@
+2010-07-22  Chris Sutcliffe  <ir0nh34d@users.sourceforge.net>
+
+	* include/basetyps.h (REFGUID, REFIID, REFCLSID, REFFMTID): Revert change
+	from 2010-07-17 since it breaks several applications.
+
 2010-07-21  Chris Sutcliffe  <ir0nh34d@users.sourceforge.net>
 
 	* lib/kernel32.def: Regenerate using gendef.
diff --git a/winsup/w32api/include/basetyps.h b/winsup/w32api/include/basetyps.h
index d9c9a03a4..b644bdf6f 100644
--- a/winsup/w32api/include/basetyps.h
+++ b/winsup/w32api/include/basetyps.h
@@ -139,6 +139,23 @@ typedef unsigned long error_status_t;
 #define uuid_t UUID
 typedef unsigned long PROPID;
 
+#ifndef _REFGUID_DEFINED
+#if defined (__cplusplus) && !defined (CINTERFACE)
+#define REFGUID const GUID&
+#define REFIID const IID&
+#define REFCLSID const CLSID&
+#define REFFMTID const FMTID&
+#else
+#define REFGUID const GUID* const
+#define REFIID const IID* const
+#define REFCLSID const CLSID* const
+#define REFFMTID const FMTID* const
+#endif
+#define _REFGUID_DEFINED
+#define _REFIID_DEFINED
+#define _REFCLSID_DEFINED
+#define _REFFMTID_DEFINED
+#endif
 #ifndef GUID_SECTION
 #define GUID_SECTION ".text"
 #endif