How do I pass va_list to wsprintfW()?

I'm trying to make a custom printf-like function that take the arguments, format then display on MessageBox but wsprintfW isn't working properly, it display some chinese characters, I think the encoding messed up somewhere but I can't see where. How to fix that?

the code:

void panic(const wchar_t *fmt, ...)
{
    wchar_t buffer[1024];
    va_list args = NULL;
    va_start(args, fmt);
    wsprintfW(buffer, fmt, args);
    va_end(args);
    MessageBoxW(NULL, buffer, L"error", MB_OK | MB_ICONERROR);
    ExitProcess(EXIT_FAILURE);
}

calling from:

panic(L"hello, %s!", L"michael");

return error:

You need to use the wvsprintfW function. (Note the "v" second letter in the function name.)

void panic(const wchar_t *fmt, ...)
{
    wchar_t buffer[1024];
    va_list args = NULL;
    va_start(args, fmt);
    wvsprintfW(buffer, fmt, args);
    va_end(args);
    MessageBoxW(NULL, buffer, L"error", MB_OK | MB_ICONERROR);
    ExitProcess(EXIT_FAILURE);
}