utf-8 strings in ncursesw with c-wrapper

Hi.  I'm trying to use ncursesw with c-wrapper, with a preamble like:

    (use c-wrapper)
    (c-load "ncursesw/ncurses.h" :libs "-lncursesw")

And this works:

    (initscr)
    (mvaddstr 0 0 "Hello, world！")
    (refresh)
    (endwin)

But this results in mojibake:

    (initscr)
    (mvaddstr 0 0 "こんにちは、世界！")
    (refresh)
    (endwin)

The C version works if I call setlocale before starting:

    #include <ncursesw/ncurses.h>
    #include <locale.h>

    int main(void)
    {
            setlocale(LC_CTYPE, "en_US.UTF-8");
            initscr();
            mvaddstr(0, 0, "こんにちは世界！");
            refresh();