Memory leak?

Running the homepage example with cargo run on macOSX (last stable version of rust):

extern crate piston_window;

use piston_window::*;

fn main() {
    let mut window: PistonWindow =
        WindowSettings::new("Hello Piston!", [640, 480])
        .exit_on_esc(true).build().unwrap();
    while let Some(e) = window.next() {
        window.draw_2d(&e, |c, g| {
            clear([1.0; 4], g);
            rectangle([1.0, 0.0, 0.0, 1.0], // red
                      [0.0, 0.0, 100.0, 100.0],
                      c.transform, g);
        });
    }
}

Memory consumption starts to 17 MB and slowly increases while the program runs. Is it normal?

Start with the supplied Rust homepage example and reproduce the reported memory growth on macOS while monitoring usage. Done means determining whether the increase is expected; if not, identify the affected component and provide a focused reproduction or fix.