Will pyglet draw a line at y = 0?

windows 10/pyglet 1.5.26.

I'm unable to convince pyglet to draw a (visible) line with both vertices having a y-coordinate = 0. This does not seem to be a problem with other primitives:

from pyglet import shapes


class DrawingWindow(pyglet.window.Window):

    def __init__(self):

        super(DrawingWindow, self).__init__(300, 300)
        self.batch = pyglet.graphics.Batch()

    def on_draw(self):

        # this red line is not visible:
        l0 = shapes.Line(0, 0, 300, 0, color=(255, 0, 0), batch=self.batch)

        # this blue one is (note y-coordinate), though it appears to have y-coordinates = 0:
        l1 = shapes.Line(0, 1, 200, 0, color=(0, 0, 255), batch=self.batch)

        # and this green-bordered rectangle is OK too:
        square = shapes.BorderedRectangle(0, 0, 100, 100,
                                          border=1, color=(255, 255, 255),
                                          border_color=(0, 255, 0), batch=self.batch)

        self.clear()
        self.batch.draw()


if __name__ == '__main__':
    window = DrawingWindow()
    pyglet.app.run()```


I've tried this with a simple pyglet.draw(...) call with the same result.