custom css background image not recognised even after .ms-backgroundImage override

I have a custom html master page, with its own stylesheet, on which the footer has background image set to them. The CSS is below. But sharepoint 2013 doesnt recognise this background image. I dont think the url is wrong as every other image on the page works. Can someone please help with this ?

.spfooter.ms-backgroundImage
{
background-image:url('Images/bottombg.png');
}