diff --git a/libpsx/include/stdio.h b/libpsx/include/stdio.h
index 88e7afb..0ea5828 100644
--- a/libpsx/include/stdio.h
+++ b/libpsx/include/stdio.h
@@ -19,6 +19,7 @@
 
 #include <stdarg.h>
 #include <stdbool.h>
+#include <stddef.h>
 
 #ifdef __cplusplus
 extern "C"
@@ -31,11 +32,6 @@ extern "C"
 
 #define EOF		-1
 
-/* NULL */
-#ifndef NULL
-#define NULL (void*)0
-#endif
-
 enum stdio_directions
 {
 	STDIO_DIRECTION_BIOS,