diff --git a/reactos/include/dxsdk/amaudio.h b/reactos/include/dxsdk/amaudio.h
index 242b444c7bb..4390424705a 100644
--- a/reactos/include/dxsdk/amaudio.h
+++ b/reactos/include/dxsdk/amaudio.h
@@ -26,6 +26,7 @@ DECLARE_INTERFACE_(IAMDirectSound,IUnknown)
   STDMETHOD(SetFocusWindow)(THIS_ HWND, BOOL) PURE ;
   STDMETHOD(GetFocusWindow)(THIS_ HWND *, BOOL*) PURE ;
 };
+#undef INTERFACE
 
 #ifdef __cplusplus
 }