You can potentially get around this using a separate element and position: fixed
which does work!
HTML:
<div id="Background"></div>
<div id="Content"></div>
CSS:
#Background {
background: #000 url("img/Background.jpg") no-repeat 50% 0;
position: fixed;
top: 0;
left: 0;
right: 0;
bottom: 0;
z-index: -1
}