diff --git a/firmware/libc/include/string.h b/firmware/libc/include/string.h
index d84c3e3..f4914ea 100644
--- a/firmware/libc/include/string.h
+++ b/firmware/libc/include/string.h
@@ -13,18 +13,9 @@
 
 #include "_ansi.h"
 
-#if !defined(__size_t_defined)&& !defined(_SIZE_T_) && !defined(size_t) && !defined(_SIZE_T_DECLARED)
-#define __size_t_defined
-#define _SIZE_T
-#define _SIZE_T_
-#define _SIZE_T_DECLARED
-#define size_t size_t
-typedef unsigned long size_t;
-#endif
-
-#ifndef NULL
-#define NULL ((void*)0)
-#endif
+#define __need_size_t
+#define __need_NULL
+#include <stddef.h>
 
 _PTR     _EXFUN(memchr,(const _PTR, int, size_t));
 int      _EXFUN(memcmp,(const _PTR, const _PTR, size_t));