diff --git a/include/polarssl/arc4.h b/include/polarssl/arc4.h
index 6c9788c..96e520d 100644
--- a/include/polarssl/arc4.h
+++ b/include/polarssl/arc4.h
@@ -30,7 +30,7 @@
 #include POLARSSL_CONFIG_FILE
 #endif
 
-#include <string.h>
+#include <stddef.h>
 
 #if !defined(POLARSSL_ARC4_ALT)
 // Regular implementation