diff --git a/src/lib/include/fwts_uefi.h b/src/lib/include/fwts_uefi.h
index 64e72c1..e25da50 100644
--- a/src/lib/include/fwts_uefi.h
+++ b/src/lib/include/fwts_uefi.h
@@ -46,7 +46,8 @@ enum {
 	FWTS_UEFI_TIME_IN_DAYLIGHT = 		0x02
 };
 
-#define HIGH_BIT_SET	(1UL << 63)
+#define BITS_PER_UINT64          	(sizeof(long) * 8)
+#define HIGH_BIT_SET			(1UL << (BITS_PER_UINT64-1))
 
 #define EFI_SUCCESS			0
 #define EFI_LOAD_ERROR			(1 | HIGH_BIT_SET)