YUI Dialog max height

HTML

<script src="http://ajax.googleapis.com/ajax/libs/yui/2.9.0/build/yahoo-dom-event/yahoo-dom-event.js"></script>
<script src="http://ajax.googleapis.com/ajax/libs/yui/2.9.0/build/container/container-min.js"></script>
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/yui/2.9.0/build/container/assets/skins/sam/container.css">
<div id="my-dialog" class="yui-pe-content">
    <div class="hd">Title</div>
    <div class="bd"/>
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</div>

CSS

.bd { overflow: scroll } /* Has no effect */
body  { font-family: sans-serif }

JavaScript

var Event = YAHOO.util.Event;

Event.onDOMReady(function() {
    var myDialog = new YAHOO.widget.Dialog("my-dialog", { 
        width : "300px", fixedcenter: true });
    
    // For testing, add some long content to the dialog
    for (var i = 1; i <= 50; i++)
        myDialog.body.innerHTML += "<div>" + i + "</div>";

    myDialog.render();
    myDialog.show();    
    
    var maxHeight = 
        YAHOO.util.Dom.getViewportHeight()
        - (myDialog.element.clientHeight - myDialog.body.clientHeight)
        - 40;

    myDialog.body.style.maxHeight = maxHeight + "px";
    
});