diff --git a/Source/kwsys/testSystemTools.cxx b/Source/kwsys/testSystemTools.cxx
index 5070df4118..a7002e10b4 100644
--- a/Source/kwsys/testSystemTools.cxx
+++ b/Source/kwsys/testSystemTools.cxx
@@ -351,7 +351,7 @@ static bool CheckFileOperations()
   // While we're at it, check proper TestFileAccess functionality.
   bool do_write_test = true;
 #if defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__) ||     \
-  defined(__NetBSD__) || defined(__DragonFly__) || defined(__HOS_AIX__)
+  defined(__NetBSD__) || defined(__DragonFly__) || defined(_AIX)
   // If we are running as root on POSIX-ish systems (Linux and the BSDs,
   // at least), ignore this check, as root can always write to files.
   do_write_test = (getuid() != 0);