Un-wanted slideUp behavior

The wrapper narrows at the end of the animation.

HTML

<div style="float: left; border: 1px solid" class="wrapper">
<div class="header">
    Short header (click)
</div>
<div class="content">
    Long-ish content. To some extent.
</div>
</div>

JavaScript

$('.wrapper').each(function() {
    var wrapper = this;
    $('.header', wrapper).click(function() {
        $('.content', wrapper).slideToggle();
    });
});