Index: uspace/lib/c/include/stddef.h
===================================================================
--- uspace/lib/c/include/stddef.h	(revision 8ddaaacd4f1ffc7cd429e863b42a92bfe0fbf899)
+++ uspace/lib/c/include/stddef.h	(revision c9f3e7e90bf5ef1a7d8f76f8717c35a796152375)
@@ -43,7 +43,5 @@
 #include <_bits/wchar_t.h>
 
-#ifndef NULL
-	#define NULL  ((void *) 0)
-#endif
+#include <_bits/NULL.h>
 
 #define offsetof(type, member) \
Index: uspace/lib/posix/include/posix/locale.h
===================================================================
--- uspace/lib/posix/include/posix/locale.h	(revision 8ddaaacd4f1ffc7cd429e863b42a92bfe0fbf899)
+++ uspace/lib/posix/include/posix/locale.h	(revision c9f3e7e90bf5ef1a7d8f76f8717c35a796152375)
@@ -40,7 +40,5 @@
 #endif
 
-#ifndef NULL
-	#define NULL ((void *) 0)
-#endif
+#include <_bits/NULL.h>
 
 #ifndef __locale_t_defined
Index: uspace/lib/posix/include/posix/stddef.h
===================================================================
--- uspace/lib/posix/include/posix/stddef.h	(revision 8ddaaacd4f1ffc7cd429e863b42a92bfe0fbf899)
+++ uspace/lib/posix/include/posix/stddef.h	(revision c9f3e7e90bf5ef1a7d8f76f8717c35a796152375)
@@ -42,7 +42,5 @@
 #include "sys/types.h"
 
-#ifndef NULL
-	#define NULL  ((void *) 0)
-#endif
+#include <_bits/NULL.h>
 
 #define offsetof(type,member) ((size_t) &(((type *) 0)->member))
Index: uspace/lib/posix/include/posix/stdlib.h
===================================================================
--- uspace/lib/posix/include/posix/stdlib.h	(revision 8ddaaacd4f1ffc7cd429e863b42a92bfe0fbf899)
+++ uspace/lib/posix/include/posix/stdlib.h	(revision c9f3e7e90bf5ef1a7d8f76f8717c35a796152375)
@@ -43,7 +43,5 @@
 #include "sys/types.h"
 
-#ifndef NULL
-	#define NULL  ((void *) 0)
-#endif
+#include <_bits/NULL.h>
 
 #define RAND_MAX  714025
Index: uspace/lib/posix/include/posix/string.h
===================================================================
--- uspace/lib/posix/include/posix/string.h	(revision 8ddaaacd4f1ffc7cd429e863b42a92bfe0fbf899)
+++ uspace/lib/posix/include/posix/string.h	(revision c9f3e7e90bf5ef1a7d8f76f8717c35a796152375)
@@ -51,7 +51,5 @@
  */
 
-#ifndef NULL
-	#define NULL  ((void *) 0)
-#endif
+#include <_bits/NULL.h>
 
 /*
Index: uspace/lib/posix/include/posix/time.h
===================================================================
--- uspace/lib/posix/include/posix/time.h	(revision 8ddaaacd4f1ffc7cd429e863b42a92bfe0fbf899)
+++ uspace/lib/posix/include/posix/time.h	(revision c9f3e7e90bf5ef1a7d8f76f8717c35a796152375)
@@ -43,7 +43,5 @@
 #include "sys/types.h"
 
-#ifndef NULL
-	#define NULL  ((void *) 0)
-#endif
+#include <_bits/NULL.h>
 
 #ifndef CLOCKS_PER_SEC