diff --git a/mingw-w64-headers/include/ChangeLog b/mingw-w64-headers/include/ChangeLog
index 4590409..4211a56 100644
--- a/mingw-w64-headers/include/ChangeLog
+++ b/mingw-w64-headers/include/ChangeLog
@@ -1,5 +1,8 @@
 2009-08-17  Kai Tietz  <kai.tietz@oenvision.com>
 
+	* io.h (_POSIX): Invert logic about !defined(_POSIX) and _POSIX
+	extension in #if guards.
+
 	* wchar.h (wmemchr): Avoid use of NULL for C++ sake to have not
 	type failures about wchar_t and void.
 	(wmemcmp): Likewise.
diff --git a/mingw-w64-headers/include/io.h b/mingw-w64-headers/include/io.h
index fd06952..a958c19 100644
--- a/mingw-w64-headers/include/io.h
+++ b/mingw-w64-headers/include/io.h
@@ -1,4 +1,3 @@
-
 /**
  * This file has no copyright assigned and is placed in the Public Domain.
  * This file is part of the w64 mingw-runtime package.
@@ -12,8 +11,6 @@
 
 #pragma pack(push,_CRT_PACKING)
 
-#ifndef _POSIX_
-
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -296,7 +293,6 @@
 #endif /* _INTEGRAL_MAX_BITS >= 64 */
 
 #ifndef NO_OLDNAMES
-
 #ifndef _UWIN
   int __cdecl chdir (const char *);
   char *__cdecl getcwd (char *, int);
@@ -305,7 +301,6 @@
   int __cdecl rmdir (const char*);
   int __cdecl chmod (const char *, int);
 #endif /* _UWIN */
-
 #endif /* Not NO_OLDNAMES */
 
   _CRTIMP errno_t __cdecl _sopen_s(int *_FileHandle,const char *_Filename,int _OpenFlag,int _ShareFlag,int _PermissionMode);
@@ -368,14 +363,7 @@
   int __cdecl write(int _Filehandle,const void *_Buf,unsigned int _MaxCharCount);
 #endif
 
-#ifdef __cplusplus
-}
-#endif
-#endif
-
-#ifdef __cplusplus
-extern "C" {
-#endif
+#ifdef _POSIX
 
 /* Misc stuff */
 char *getlogin(void);
@@ -383,6 +371,8 @@
 unsigned int alarm(unsigned int seconds);
 #endif
 
+#endif
+
 #ifdef __USE_MINGW_ACCESS
 /*  Old versions of MSVCRT access() just ignored X_OK, while the version
     shipped with Vista, returns an error code.  This will restore the