diff --git a/nwcrypt.c b/nwcrypt.c
index da276d0..8c1bcee 100644
--- a/nwcrypt.c
+++ b/nwcrypt.c
@@ -87,6 +87,8 @@ GPL. If anybody who knows more about copyright and sees any problems
 with this, please tell me.
 ****************************************************************************/
 
+#include <string.h>
+
 /******************* Data types ***************************/
 typedef unsigned char buf32[32];
 typedef unsigned char buf16[16];