diff --git a/include/D3D12MemAlloc.h b/include/D3D12MemAlloc.h
index 6b11a99..4bf64ee 100644
--- a/include/D3D12MemAlloc.h
+++ b/include/D3D12MemAlloc.h
@@ -59,9 +59,12 @@ Documentation of all members: D3D12MemAlloc.h
 */
 
 // If using this library on a platform different than Windows PC or want to use different version of DXGI,
-// you should include D3D12-compatible headers before this library on your own and define this macro.
+// you should include D3D12-compatible headers before this library on your own and define 
+// D3D12MA_D3D12_HEADERS_ALREADY_INCLUDED.
+// Alternatively, if you are targeting the open sourced DirectX headers, defining D3D12MA_USING_DIRECTX_HEADERS
+// will include them rather the ones provided by the Windows SDK.
 #ifndef D3D12MA_D3D12_HEADERS_ALREADY_INCLUDED
-    #if defined(USING_DIRECTX_HEADERS)
+    #if defined(D3D12MA_USING_DIRECTX_HEADERS)
         #include <directx/d3d12.h>
         #include <dxguids/dxguids.h>
     #else