diff --git a/libSYS/include/machine_type.h b/libSYS/include/machine_type.h
index b5642b2..d04a8e8 100644
--- a/libSYS/include/machine_type.h
+++ b/libSYS/include/machine_type.h
@@ -173,7 +173,7 @@
 
 
 /* Define 64 bit base integer type. */
-#ifdef _WIN32
+#ifdef _MSC_VER
   typedef __int64 INT64;
   typedef unsigned __int64 UINT64;
 #else