diff --git a/include/polarssl/sha512.h b/include/polarssl/sha512.h
index 6afb836..90b5e3e 100644
--- a/include/polarssl/sha512.h
+++ b/include/polarssl/sha512.h
@@ -30,7 +30,7 @@
 #include POLARSSL_CONFIG_FILE
 #endif
 
-#include <string.h>
+#include <stddef.h>
 
 #if defined(_MSC_VER) || defined(__WATCOMC__)
   #define UL64(x) x##ui64