Force scroll when jQuery Dialog is open

gistfile1.js

function enableScrollbar(event, ui) { 
    window.setTimeout(function() { 
        $(document)
            .unbind('mousedown.dialog-overlay')
            .unbind('mouseup.dialog-overlay'); 
    }, 100); 
}

//when calling a dialog, override the open method
$(...).dialog({
    modal: true,
    open: enableScrollbar
});