diff --git a/du2/program.c b/du2/program.c
index 538460c..2e3522c 100644
--- a/du2/program.c
+++ b/du2/program.c
@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <locale.h>
 
 #define LINESIZE 256
 #define MAXITEMS 100