Canvas, drawing of two concentric circles: Abnormal behavior?

[nic.sicily]

The following simple code draws, in addition to the two circles, also a mysterious horizontal line between the two circles. How can I solve it?

<script>
var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");
ctx.beginPath();
ctx.arc (250, 250, 200, 0, 2*Math.PI);
ctx.arc (250, 250, 180, 0, 2*Math.PI);
ctx.stroke();

</script>

[Funce]

Between beginPath and stroke is a single line as if you were holding the pen down on a piece of paper.

You're going to need to put each arc between different beginPath and stroke function calls.