Incompatible declaration of function

[Suzie999]

Perhaps mt eyes are missing something simple, but I cannot understand what is going on.
The following code produces intellisense and compile error "error C2373: 'GetHwnd' : redefinition; different type modifiers"

I have many functions in same manner, but this will not play ball.

extern "C" HWND __stdcall GetHwnd(wchar_t *);

HWND GetHwnd(wchar_t * wtitle){

    HWND wnd = FindWindow(nullptr, wtitle);

    if (!wnd) {

        return nullptr;
    }

    return wnd;
}

Anyone see my mistake/problem?
The prototype normally in header, and body in cpp.

Win 7 32, VS2010.

(edit) If I do this

extern "C" HWND __stdcall GetHwnd(wchar_t);

and leave body as it is then the code compiles fine.

(edit) sorry, I was missing something simple after all.

extern "C" HWND __stdcall GetHwnd(wchar_t *);
HWND __ stdcall GetHwnd(wchar_t * wtitle){
    HWND wnd = FindWindow(nullptr, wtitle);
    if (!wnd) {
        return nullptr;
    }
    return wnd;
}