diff --git a/lib/util.C b/lib/util.C
index eb3736c199..9b5f41f2a9 100755
--- a/lib/util.C
+++ b/lib/util.C
@@ -33,6 +33,7 @@
 #include <iostream>
 #include <locale>
 #include <fstream>
+#include <cctype>
 #include <ctype.h>
 #include <sys/types.h>
 #include <sys/stat.h>