Scalable background problem

[akira]

I just noticed that scalable backgrounds do not work as expected, is
there a workaround for this?

code snippet
#testf{
/*background-color: #ff00ff; */
background-image:url('images/bg.png');
}

#test img{
width: 100%;
height: 100%;
left: 0px;
top: 0px;
position: absolute;
z-index: 0;
}

Thanks