diff --git a/newlib/libc/include/sys/_types.h b/newlib/libc/include/sys/_types.h
index 6a2c94dd6..06ddd8329 100644
--- a/newlib/libc/include/sys/_types.h
+++ b/newlib/libc/include/sys/_types.h
@@ -119,6 +119,21 @@ typedef _off64_t _fpos64_t;
 #endif
 #endif
 
+/* Defined by GCC provided <stddef.h> */
+#undef __size_t
+
+#ifndef __machine_size_t_defined
+#ifdef __SIZE_TYPE__
+typedef __SIZE_TYPE__ __size_t;
+#else
+#if defined(__INT_MAX__) && __INT_MAX__ == 2147483647
+typedef int __size_t;
+#else
+typedef long __size_t;
+#endif
+#endif
+#endif
+
 #ifndef __machine_ssize_t_defined
 #ifdef __SIZE_TYPE__
 /* If __SIZE_TYPE__ is defined (gcc) we define ssize_t based on size_t.
diff --git a/newlib/libc/include/sys/types.h b/newlib/libc/include/sys/types.h
index 57b74ef4b..31f765e3e 100644
--- a/newlib/libc/include/sys/types.h
+++ b/newlib/libc/include/sys/types.h
@@ -56,11 +56,11 @@ typedef	quad_t *	qaddr_t;
 #ifndef __need_inttypes
 
 #define _SYS_TYPES_H
+/* <stddef.h> must be before <sys/_types.h> for __size_t considerations */
+#include <stddef.h>
 #include <sys/_types.h>
 #include <sys/_stdint.h>
 
-# include <stddef.h>
-
 #if __BSD_VISIBLE
 #include <machine/endian.h>
 #include <sys/select.h>