diff --git a/du5/program.c b/du5/program.c
index 2bcb8eb..b262aa9 100644
--- a/du5/program.c
+++ b/du5/program.c
@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdbool.h>
+#include <string.h>
 
 #define SIZE 128