diff --git a/mingw-w64-headers/include/adoctint.h b/mingw-w64-headers/include/adoctint.h
index e62a3c8..b18dbf0 100644
--- a/mingw-w64-headers/include/adoctint.h
+++ b/mingw-w64-headers/include/adoctint.h
@@ -6,9 +6,7 @@
 #ifndef _ADOCTINT_H_
 #define _ADOCTINT_H_
 
-#ifndef _INC_TCHAR
 #include <tchar.h>
-#endif
 
 #ifndef __REQUIRED_RPCNDR_H_VERSION__
 #define __REQUIRED_RPCNDR_H_VERSION__ 440
diff --git a/mingw-w64-headers/include/dskquota.h b/mingw-w64-headers/include/dskquota.h
index a70e8a5..3deb41f 100644
--- a/mingw-w64-headers/include/dskquota.h
+++ b/mingw-w64-headers/include/dskquota.h
@@ -6,17 +6,9 @@
 #ifndef __DSKQUOTA_H
 #define __DSKQUOTA_H
 
-#ifndef _WINDOWS_
 #include <windows.h>
-#endif
-
-#ifndef _OLE2_H_
 #include <ole2.h>
-#endif
-
-#ifndef _OLECTL_H_
 #include <olectl.h>
-#endif
 
 #ifdef INITGUIDS
 #include <initguid.h>
diff --git a/mingw-w64-headers/include/mapidefs.h b/mingw-w64-headers/include/mapidefs.h
index 39b195a..9f9ced6 100644
--- a/mingw-w64-headers/include/mapidefs.h
+++ b/mingw-w64-headers/include/mapidefs.h
@@ -16,10 +16,7 @@
 #ifndef _OLEERROR_H_
 #include <winerror.h>
 #endif
-#ifndef _OBJBASE_H_
 #include <objbase.h>
-#endif
-
 #include <stddef.h>
 
 #ifndef MAPI_DIM
diff --git a/mingw-w64-headers/include/oledlg.h b/mingw-w64-headers/include/oledlg.h
index 8d8b9a8..2f31820 100644
--- a/mingw-w64-headers/include/oledlg.h
+++ b/mingw-w64-headers/include/oledlg.h
@@ -18,21 +18,13 @@
 #define _UNICODE
 #endif
 
-#ifndef _WINDOWS_
 #include <windows.h>
-#endif
-#ifndef _INC_SHELLAPI
 #include <shellapi.h>
-#endif
-#ifndef _INC_COMMDLG
 #include <commdlg.h>
-#endif
-#ifndef _OLE2_H_
 #include <ole2.h>
-#endif
 #include <string.h>
 #include <tchar.h>
-#endif
+#endif /* End RC_INVOKED */
 
 #include <dlgs.h>
 
diff --git a/mingw-w64-headers/include/shlobj.h b/mingw-w64-headers/include/shlobj.h
index c6fcd00..8ec6eec 100644
--- a/mingw-w64-headers/include/shlobj.h
+++ b/mingw-w64-headers/include/shlobj.h
@@ -81,12 +81,8 @@
 #endif
 
 #include <ole2.h>
-#ifndef _PRSHT_H_
 #include <prsht.h>
-#endif
-#ifndef _INC_COMMCTRL
 #include <commctrl.h>
-#endif
 
 #ifndef INITGUID
 #include <shlguid.h>
diff --git a/mingw-w64-headers/include/sql.h b/mingw-w64-headers/include/sql.h
index 488827e..92935e4 100644
--- a/mingw-w64-headers/include/sql.h
+++ b/mingw-w64-headers/include/sql.h
@@ -10,9 +10,7 @@
 #define ODBCVER 0x0351
 #endif
 
-#ifndef __SQLTYPES
-#include "sqltypes.h"
-#endif
+#include <sqltypes.h>
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/mingw-w64-headers/include/sqlext.h b/mingw-w64-headers/include/sqlext.h
index 575e8fb..3da99cc 100644
--- a/mingw-w64-headers/include/sqlext.h
+++ b/mingw-w64-headers/include/sqlext.h
@@ -6,9 +6,7 @@
 #ifndef __SQLEXT
 #define __SQLEXT
 
-#ifndef __SQL
-#include "sql.h"
-#endif
+#include <sql.h>
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/mingw-w64-headers/include/sqloledb.h b/mingw-w64-headers/include/sqloledb.h
index d2cfea4..f0d6095 100644
--- a/mingw-w64-headers/include/sqloledb.h
+++ b/mingw-w64-headers/include/sqloledb.h
@@ -6,9 +6,7 @@
 #ifndef _SQLOLEDB_H_
 #define _SQLOLEDB_H_
 
-#ifndef __oledb_h__
-#include "oledb.h"
-#endif
+#include <oledb.h>
 
 #ifdef DBINITCONSTANTS
 extern const GUID CLSID_SQLOLEDB = {0xc7ff16cL,0x38e3,0x11d0,{0x97,0xab,0x0,0xc0,0x4f,0xc2,0xad,0x98}};
diff --git a/mingw-w64-headers/include/sspserr.h b/mingw-w64-headers/include/sspserr.h
index 3c1491c..3c78e3a 100644
--- a/mingw-w64-headers/include/sspserr.h
+++ b/mingw-w64-headers/include/sspserr.h
@@ -6,8 +6,6 @@
 #ifndef __SSPSERR_H__
 #define __SSPSERR_H__
 
-#ifndef SCARD_S_SUCCESS
-#include "scarderr.h"
-#endif
+#include <scarderr.h>
 
 #endif
diff --git a/mingw-w64-headers/include/tvout.h b/mingw-w64-headers/include/tvout.h
index 8885590..228a682 100644
--- a/mingw-w64-headers/include/tvout.h
+++ b/mingw-w64-headers/include/tvout.h
@@ -6,9 +6,7 @@
 #ifndef __TVOUT__
 #define __TVOUT__
 
-#ifndef GUID_DEFINED
 #include <guiddef.h>
-#endif
 
 typedef struct _VIDEOPARAMETERS {
   GUID Guid;
diff --git a/mingw-w64-headers/include/wabdefs.h b/mingw-w64-headers/include/wabdefs.h
index 4e61054..c9568e9 100644
--- a/mingw-w64-headers/include/wabdefs.h
+++ b/mingw-w64-headers/include/wabdefs.h
@@ -20,10 +20,7 @@
 #ifndef _OLEERROR_H_
 #include <objerror.h>
 #endif
-#ifndef _OBJBASE_H_
 #include <objbase.h>
-#endif
-
 #include <stddef.h>
 
 #ifndef MAPI_DIM
diff --git a/mingw-w64-headers/include/winldap.h b/mingw-w64-headers/include/winldap.h
index 8656934..d2e20cc 100644
--- a/mingw-w64-headers/include/winldap.h
+++ b/mingw-w64-headers/include/winldap.h
@@ -14,9 +14,7 @@
 #include <windef.h>
 #endif
 
-#ifndef _SCHNLSP_H_
 #include <schnlsp.h>
-#endif
 
 #define WINLDAPAPI DECLSPEC_IMPORT
 
diff --git a/mingw-w64-headers/include/wmiatlprov.h b/mingw-w64-headers/include/wmiatlprov.h
index db479bd..e45cca3 100644
--- a/mingw-w64-headers/include/wmiatlprov.h
+++ b/mingw-w64-headers/include/wmiatlprov.h
@@ -5,13 +5,8 @@
 #error Requires C++ compilation (use a .cpp suffix)
 #endif
 
-#ifndef __wbemprov_h__
 #include <wbemprov.h>
-#endif
-
-#ifndef __wmiutils_h__
 #include <wmiutils.h>
-#endif
 
 namespace ATL {
   class ATL_NO_VTABLE IWbemInstProviderImpl : public IWbemServices,public IWbemProviderInit {
diff --git a/mingw-w64-headers/include/ws2spi.h b/mingw-w64-headers/include/ws2spi.h
index cb2cd5c..4b6852c 100644
--- a/mingw-w64-headers/include/ws2spi.h
+++ b/mingw-w64-headers/include/ws2spi.h
@@ -10,9 +10,7 @@
 #include <pshpack4.h>
 #endif
 
-#ifndef _WINSOCK2API_
 #include <winsock2.h>
-#endif
 
 #define WSPDESCRIPTION_LEN 255
 
diff --git a/mingw-w64-headers/include/xcmcmsx2.h b/mingw-w64-headers/include/xcmcmsx2.h
index 0fda040..f0f359b 100644
--- a/mingw-w64-headers/include/xcmcmsx2.h
+++ b/mingw-w64-headers/include/xcmcmsx2.h
@@ -6,14 +6,8 @@
 #ifndef _XCMCMSX2_H
 #define _XCMCMSX2_H
 
-#ifndef XCMCMSXT_H
 #include <xcmcmsxt.h>
-#endif
-
-#ifndef MAPIDEFS_H
 #include <mapidefs.h>
-#endif
-
 #include <xcmc.h>
 
 #ifdef __cplusplus
@@ -36,3 +30,4 @@
 }
 #endif
 #endif
+
diff --git a/mingw-w64-headers/include/xlocinfo.h b/mingw-w64-headers/include/xlocinfo.h
index c1ff3bf..514ae67 100644
--- a/mingw-w64-headers/include/xlocinfo.h
+++ b/mingw-w64-headers/include/xlocinfo.h
@@ -8,9 +8,7 @@
 #include <ctype.h>
 #include <locale.h>
 #include <wchar.h>
-#ifndef _YVALS
 #include <yvals.h>
-#endif
 
 #pragma pack(push,_CRT_PACKING)
 
diff --git a/mingw-w64-headers/include/xmath.h b/mingw-w64-headers/include/xmath.h
index e3774bf..31ad43c 100644
--- a/mingw-w64-headers/include/xmath.h
+++ b/mingw-w64-headers/include/xmath.h
@@ -8,9 +8,7 @@
 #include <errno.h>
 #include <math.h>
 #include <stddef.h>
-#ifndef _YMATH
 #include <ymath.h>
-#endif
 
 _C_STD_BEGIN