[BUG] Address is not a valid IPv4 or IPv6 address

It gives me an error:

Warning: gethostbyaddr() [function.gethostbyaddr]: Address is not a valid IPv4 or IPv6 address in /xxx/xxx/append.php on line 17

If fixed it by changing

$host = gethostbyaddr($ip);

to
$host = @gethostbyaddr($ip);