diff --git a/include/stddef.h b/include/stddef.h
index 3d328daa..95c6dc79 100644
--- a/include/stddef.h
+++ b/include/stddef.h
@@ -1,5 +1,6 @@
 #ifndef _STDDEF_H
 #define _STDDEF_H
+#define _TINYC_STDDEF
 
 typedef __SIZE_TYPE__ size_t;
 typedef __PTRDIFF_TYPE__ ssize_t;
diff --git a/tests/tcctest.c b/tests/tcctest.c
index 9f920777..d40d08f5 100644
--- a/tests/tcctest.c
+++ b/tests/tcctest.c
@@ -17,10 +17,6 @@
 /* __VA_ARGS__ and __func__ support */
 #define C99_MACROS
 
-#ifndef __TINYC__
-typedef __SIZE_TYPE__ uintptr_t;
-#endif
-
 #if defined(_WIN32) \
     || (defined(__arm__) \
         && (defined(__FreeBSD__) \
@@ -66,6 +62,10 @@ typedef __SIZE_TYPE__ uintptr_t;
 
 #include "tcctest.h"
 
+#ifndef _TINYC_STDDEF
+#include <stdint.h>
+#endif
+
 /* Test two more ways to include a file named like a pp-number */
 #define INC(name) <tests/name.h>
 #define funnyname 42test.h