__stat64, redefinition; different type when including sys\stat.h after wchar.h

#include<windows.h>
#include<wchar.h>
__stat64 a;
#include<sys\stat.h>
__stat64 b;// <-- compiler error


Example compiler output:

d:\temp\t3test1\t3test1\stdafx.h(20) : error C2146: syntax error : missing ';' before identifier 'b'
d:\temp\t3test1\t3test1\stdafx.h(20) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
d:\temp\t3test1\t3test1\stdafx.h(20) : error C2373: '_stat64' : redefinition; different type modifiers
c:\program files\microsoft visual studio 8\vc\include\sys\stat.h(237) : see declaration of '_stat64'
d:\temp\t3test1\t3test1\stdafx.h(20) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int