diff --git a/include/lib/libc/stdio.h b/include/lib/libc/stdio.h
index 3d9323e..2d9e655 100644
--- a/include/lib/libc/stdio.h
+++ b/include/lib/libc/stdio.h
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 /*
- * Portions copyright (c) 2018, ARM Limited and Contributors.
+ * Portions copyright (c) 2018-2019, ARM Limited and Contributors.
  * All rights reserved.
  */
 
@@ -12,12 +12,9 @@
 #define STDIO_H
 
 #include <cdefs.h>
+#include <stddef.h>
 #include <stdio_.h>
 
-#ifndef NULL
-#define NULL ((void *) 0)
-#endif
-
 #define EOF            -1
 
 int printf(const char *fmt, ...) __printflike(1, 2);