Index: head/include/stddef.h
===================================================================
--- head/include/stddef.h
+++ head/include/stddef.h
@@ -62,7 +62,7 @@
 #endif
 #endif
 
-#if __STDC_VERSION__ >= 201112L || __cplusplus >= 201103L
+#if __ISO_C_VISIBLE >= 2011 || __cplusplus >= 201103L
 #ifndef __CLANG_MAX_ALIGN_T_DEFINED
 typedef	__max_align_t	max_align_t;
 #define __CLANG_MAX_ALIGN_T_DEFINED