XF 1.5 Weird Zoom out on background

[Aberidius]

When i zoom out from the page, the background leaves that massive amount of space down there. Anyone who has an idea why?

background:#000 url(http://vignette2.wikia.nocookie.net/metro2033/images/5/59/Depot.jpg/revision/latest?cb=20110520042955) no-repeat;
    background-size:cover;
    -moz-background-size:cover;
    -o-background-size:cover;
    -webkit-background-size:cover;
    background-attachment:fixed;