diff --git a/mingw-w64-headers/include/dxva2api.h b/mingw-w64-headers/include/dxva2api.h
index c75474e..ca30c74 100644
--- a/mingw-w64-headers/include/dxva2api.h
+++ b/mingw-w64-headers/include/dxva2api.h
@@ -278,7 +278,7 @@
   DXVA2_Fixed32 StepSize;
 } DXVA2_ValueRange;
 
-#ifdef _D3D9_H
+#ifdef _D3D9_H_
 typedef struct _DXVA2_VideoDesc {
   UINT                 SampleWidth;
   UINT                 SampleHeight;
@@ -359,7 +359,7 @@
   DWORD                DestData;
 } DXVA2_VideoProcessBltParams;
 
-#ifdef _D3D9_H
+#ifdef _D3D9_H_
 typedef struct _DXVA2_VideoProcessorCaps {
   UINT    DeviceCaps;
   D3DPOOL InputPool;
@@ -380,7 +380,7 @@
 DXVA2_SampleData_RFF_TFF_Present
 */
 
-#ifdef _D3D9_H
+#ifdef _D3D9_H_
 typedef struct _DXVA2_VideoSample {
   REFERENCE_TIME       Start;
   REFERENCE_TIME       End;
@@ -434,7 +434,7 @@
   return f32;
 }
 
-#ifdef _D3D9_H
+#ifdef _D3D9_H_
 HRESULT WINAPI DXVA2CreateDirect3DDeviceManager9(UINT *pResetToken,IDirect3DDeviceManager9 **ppDXVAManager);
 HRESULT WINAPI DXVA2CreateVideoService(IDirect3DDevice9 *pDD,REFIID riid,void **ppService);
 /*****************************************************************************
diff --git a/mingw-w64-headers/include/dxva2api.idl b/mingw-w64-headers/include/dxva2api.idl
index 038d6b6..007a2e4 100644
--- a/mingw-w64-headers/include/dxva2api.idl
+++ b/mingw-w64-headers/include/dxva2api.idl
@@ -257,7 +257,7 @@
 cpp_quote("  DXVA2_Fixed32 StepSize;")
 cpp_quote("} DXVA2_ValueRange;")
 cpp_quote("")
-cpp_quote("#ifdef _D3D9_H")
+cpp_quote("#ifdef _D3D9_H_")
 cpp_quote("typedef struct _DXVA2_VideoDesc {")
 cpp_quote("  UINT                 SampleWidth;")
 cpp_quote("  UINT                 SampleHeight;")
@@ -338,7 +338,7 @@
 cpp_quote("  DWORD                DestData;")
 cpp_quote("} DXVA2_VideoProcessBltParams;")
 cpp_quote("")
-cpp_quote("#ifdef _D3D9_H")
+cpp_quote("#ifdef _D3D9_H_")
 cpp_quote("typedef struct _DXVA2_VideoProcessorCaps {")
 cpp_quote("  UINT    DeviceCaps;")
 cpp_quote("  D3DPOOL InputPool;")
@@ -359,7 +359,7 @@
 cpp_quote("DXVA2_SampleData_RFF_TFF_Present")
 cpp_quote("*/")
 cpp_quote("")
-cpp_quote("#ifdef _D3D9_H")
+cpp_quote("#ifdef _D3D9_H_")
 cpp_quote("typedef struct _DXVA2_VideoSample {")
 cpp_quote("  REFERENCE_TIME       Start;")
 cpp_quote("  REFERENCE_TIME       End;")
@@ -413,7 +413,7 @@
 cpp_quote("  return f32;")
 cpp_quote("}")
 cpp_quote("")
-cpp_quote("#ifdef _D3D9_H")
+cpp_quote("#ifdef _D3D9_H_")
 cpp_quote("HRESULT WINAPI DXVA2CreateDirect3DDeviceManager9(UINT *pResetToken,IDirect3DDeviceManager9 **ppDXVAManager);")
 cpp_quote("HRESULT WINAPI DXVA2CreateVideoService(IDirect3DDevice9 *pDD,REFIID riid,void **ppService);")