diff --git a/mingw-w64-headers/include/winnt.h b/mingw-w64-headers/include/winnt.h
index 10ed110..8cd8de1 100644
--- a/mingw-w64-headers/include/winnt.h
+++ b/mingw-w64-headers/include/winnt.h
@@ -995,11 +995,11 @@
     }
 #ifdef _WIN64
     __CRT_INLINE BOOLEAN _BitScanForward64(DWORD *Index,DWORD64 Mask) {
-      __asm__ __volatile__("bsfq %1,%0" : "=r" (Mask),"=m" ((*(volatile DWORD64 *)Index)));
+      __asm__ __volatile__("bsfq %1,%0" : "=r" (Mask),"=m" ((*(volatile LONG64 *)Index)));
       return Mask!=0;
     }
     __CRT_INLINE BOOLEAN _BitScanReverse64(DWORD *Index,DWORD64 Mask) {
-      __asm__ __volatile__("bsrq %1,%0" : "=r" (Mask),"=m" ((*(volatile DWORD64 *)Index)));
+      __asm__ __volatile__("bsrq %1,%0" : "=r" (Mask),"=m" ((*(volatile LONG64 *)Index)));
       return Mask!=0;
     }
 #endif