Sorting Properties Listing by Asc. Price [SOLVED]

Hi,
I'm trying to sort properties listing by ascending price but I can't.
Item Menu is set as Sort by Price and Order Ascending but nothing changes.

I have changed components > com_osproperty > classes > listing.php line

if($orderby == ""){
$orderby = "a.id";
}

to

if($orderby == ""){
$orderby = "a.price";
}

but doesn´t work...

Any idea??

Thanks