diff --git a/dll/arcfour/md5.c b/dll/arcfour/md5.c
index df0cc3b..a1627eb 100644
--- a/dll/arcfour/md5.c
+++ b/dll/arcfour/md5.c
@@ -1,5 +1,6 @@
 /* MD5 Message Digest algorithm */
 
+#include <string.h>
 #include "md5.h"
 
 /* Prototypes */