jQuery SVG, why can’t I addClass?

I am using jQuery SVG. I can’t add or remove a class to an object. Anyone know my mistake?

The SVG:

<rect class="jimmy" id="p5" x="200" y="200" width="100" height="100" />

The jQuery that won’t add the class:

$(".jimmy").click(function() {
    $(this).addClass("clicked");
});

I know the SVG and jQuery are working together fine because I can target the object and fire an alert when it’s clicked:

$(".jimmy").click(function() {
    alert('Handler for .click() called.');
});