diff --git a/mingw-w64-headers/include/winnt.h b/mingw-w64-headers/include/winnt.h
index 1cd78a2..4da36dd 100644
--- a/mingw-w64-headers/include/winnt.h
+++ b/mingw-w64-headers/include/winnt.h
@@ -256,7 +256,11 @@
 #endif
 #endif /* FASTCALL */
 
+#if defined(_ARM_)
+#define NTAPI
+#else
 #define NTAPI __stdcall
+#endif
 #define NTAPI_INLINE NTAPI
 
 #if !defined(_NTSYSTEM_)