FileReader not working inside Iframe

I try to show a preview (thumb) of selected files (and then upload) but FileReader is not working when inside an Iframe

It works very well if not inside an Iframe

I'm using IE11 on Win 8.1 (works on Chrome 38 and FF 33)

<script type="text/javascript">

try {
	var reader = new FileReader();
} catch(e) {
	alert(e.message);
}

</script>