C++ ncurses: printw with special characters yeilds '�~T~B'

Question

I'm trying to print box drawing characters with ncurses in C++, as shown below.

#include <iostream>
#include <ncurses.h>

int main() {
    initscr();
    addstr("│");
    getch();
    endwin();
}

When I use printw or addstr to print non-alphabetic/numeric to the screen, it only prints �~T~B. What am I doing wrong?