diff --git a/include/lib/libc/aarch32/stdio_.h b/include/lib/libc/aarch32/stdio_.h
index 50d3cc2ed91f166b76abc9aaa5dc087ef369df70..5e49425cbb7d06c648e9cb79c30cd930e25c0b65 100644
--- a/include/lib/libc/aarch32/stdio_.h
+++ b/include/lib/libc/aarch32/stdio_.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2018-2019, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -7,11 +7,6 @@
 #ifndef STDIO__H
 #define STDIO__H
 
-#ifndef SIZET_
-typedef unsigned int size_t;
-#define SIZET_
-#endif
-
 #ifndef SSIZET_
 typedef int ssize_t;
 #define SSIZET_
diff --git a/include/lib/libc/aarch32/stdlib_.h b/include/lib/libc/aarch32/stdlib_.h
deleted file mode 100644
index ff53b6f923b962a1ca2afffdd2b96df11f150fa2..0000000000000000000000000000000000000000
--- a/include/lib/libc/aarch32/stdlib_.h
+++ /dev/null
@@ -1,15 +0,0 @@
-/*
- * Copyright (c) 2018-2019, ARM Limited and Contributors. All rights reserved.
- *
- * SPDX-License-Identifier: BSD-3-Clause
- */
-
-#ifndef STDLIB__H
-#define STDLIB__H
-
-#ifndef SIZET_
-typedef unsigned int size_t;
-#define SIZET_
-#endif
-
-#endif /* STDLIB__H */
diff --git a/include/lib/libc/aarch32/string_.h b/include/lib/libc/aarch32/string_.h
deleted file mode 100644
index 4e139b0db87328d769bf66fc7308802565ed25e4..0000000000000000000000000000000000000000
--- a/include/lib/libc/aarch32/string_.h
+++ /dev/null
@@ -1,15 +0,0 @@
-/*
- * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
- *
- * SPDX-License-Identifier: BSD-3-Clause
- */
-
-#ifndef STRING__H
-#define STRING__H
-
-#ifndef SIZET_
-typedef unsigned int size_t;
-#define SIZET_
-#endif
-
-#endif /* STRING__H */
diff --git a/include/lib/libc/aarch32/time_.h b/include/lib/libc/aarch32/time_.h
deleted file mode 100644
index cfd487dc6f189813aed5f98cd67da02debdddc98..0000000000000000000000000000000000000000
--- a/include/lib/libc/aarch32/time_.h
+++ /dev/null
@@ -1,15 +0,0 @@
-/*
- * Copyright (c) 2018-2019, ARM Limited and Contributors. All rights reserved.
- *
- * SPDX-License-Identifier: BSD-3-Clause
- */
-
-#ifndef TIME__H
-#define TIME__H
-
-#ifndef SIZET_
-typedef unsigned int size_t;
-#define SIZET_
-#endif
-
-#endif /* TIME__H */
diff --git a/include/lib/libc/aarch64/stdio_.h b/include/lib/libc/aarch64/stdio_.h
index 09b0172dd13a116e1bdc880c13f1bbbcd6543e86..afaeadc21819e027ae158f9b2e4eeb28e135299c 100644
--- a/include/lib/libc/aarch64/stdio_.h
+++ b/include/lib/libc/aarch64/stdio_.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2018-2019, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -7,11 +7,6 @@
 #ifndef STDIO__H
 #define STDIO__H
 
-#ifndef SIZET_
-typedef unsigned long size_t;
-#define SIZET_
-#endif
-
 #ifndef SSIZET_
 typedef long ssize_t;
 #define SSIZET_
diff --git a/include/lib/libc/aarch64/stdlib_.h b/include/lib/libc/aarch64/stdlib_.h
deleted file mode 100644
index 531308a2e63f58825bb7ea4ef6c03b0a9c2e2ce8..0000000000000000000000000000000000000000
--- a/include/lib/libc/aarch64/stdlib_.h
+++ /dev/null
@@ -1,15 +0,0 @@
-/*
- * Copyright (c) 2018-2019, ARM Limited and Contributors. All rights reserved.
- *
- * SPDX-License-Identifier: BSD-3-Clause
- */
-
-#ifndef STDLIB__H
-#define STDLIB__H
-
-#ifndef SIZET_
-typedef unsigned long size_t;
-#define SIZET_
-#endif
-
-#endif /* STDLIB__H */
diff --git a/include/lib/libc/aarch64/string_.h b/include/lib/libc/aarch64/string_.h
deleted file mode 100644
index 71c51a6cd77766e0013ea891f44fda445dfb3bff..0000000000000000000000000000000000000000
--- a/include/lib/libc/aarch64/string_.h
+++ /dev/null
@@ -1,15 +0,0 @@
-/*
- * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
- *
- * SPDX-License-Identifier: BSD-3-Clause
- */
-
-#ifndef STRING__H
-#define STRING__H
-
-#ifndef SIZET_
-typedef unsigned long size_t;
-#define SIZET_
-#endif
-
-#endif /* STRING__H */
diff --git a/include/lib/libc/aarch64/time_.h b/include/lib/libc/aarch64/time_.h
deleted file mode 100644
index 8b298a39d7d83c867935fa21025e81069c5c4629..0000000000000000000000000000000000000000
--- a/include/lib/libc/aarch64/time_.h
+++ /dev/null
@@ -1,15 +0,0 @@
-/*
- * Copyright (c) 2018-2019, ARM Limited and Contributors. All rights reserved.
- *
- * SPDX-License-Identifier: BSD-3-Clause
- */
-
-#ifndef TIME__H
-#define TIME__H
-
-#ifndef SIZET_
-typedef unsigned long size_t;
-#define SIZET_
-#endif
-
-#endif /* TIME__H */
diff --git a/include/lib/libc/stdio.h b/include/lib/libc/stdio.h
index 3d9323efa508bd265545be17f29228287ad1a309..2d9e6557b0751e8665afe534001cac82008b930c 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);
diff --git a/include/lib/libc/stdlib.h b/include/lib/libc/stdlib.h
index 84ba37f9a419c0025f5ad3d709eff6f5e2e9ba47..24e7bae2f82293d568d1ba723ba90ceaf4d41b05 100644
--- a/include/lib/libc/stdlib.h
+++ b/include/lib/libc/stdlib.h
@@ -11,15 +11,11 @@
 #ifndef STDLIB_H
 #define STDLIB_H
 
-#include <stdlib_.h>
+#include <stddef.h>
 
 #define EXIT_FAILURE 1
 #define EXIT_SUCCESS 0
 
-#ifndef NULL
-#define NULL ((void *) 0)
-#endif
-
 #define _ATEXIT_MAX 1
 
 extern void abort(void);
diff --git a/include/lib/libc/string.h b/include/lib/libc/string.h
index ee6eeacef94eceed811a76bb0cc7bf5c15807b81..c92b6808c413f7783062acd5b05cabf0d1ad7514 100644
--- a/include/lib/libc/string.h
+++ b/include/lib/libc/string.h
@@ -4,18 +4,14 @@
  * 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.
  */
 
 #ifndef STRING_H
 #define STRING_H
 
-#include <string_.h>
-
-#ifndef NULL
-#define NULL ((void *) 0)
-#endif
+#include <stddef.h>
 
 void *memcpy(void *dst, const void *src, size_t len);
 void *memmove(void *dst, const void *src, size_t len);
diff --git a/include/lib/libc/time.h b/include/lib/libc/time.h
index 714884b05e6d44e43290a0d6b645549b7fad3667..c1c95e586396c6dd9174c8fc641212cae62e05b0 100644
--- a/include/lib/libc/time.h
+++ b/include/lib/libc/time.h
@@ -11,12 +11,8 @@
 #ifndef TIME_H
 #define TIME_H
 
-#include <time_.h>
+#include <stddef.h>
 
 typedef long int time_t;
 
-#ifndef NULL
-#define NULL ((void *) 0)
-#endif
-
 #endif /* TIME_H */