diff --git a/phpBB/includes/functions_user.php b/phpBB/includes/functions_user.php
index a44b92dd8d..9e136cc1ff 100644
--- a/phpBB/includes/functions_user.php
+++ b/phpBB/includes/functions_user.php
@@ -1470,16 +1470,10 @@ function user_ipwhois($ip)
 
 	$ipwhois = '';
 
-	if (!filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6))
-	{
-		// Limit the query to all possible flags (whois.arin.net)
-		$ip = 'z ' . $ip;
-	}
-
 	if (($fsk = @fsockopen($whois_host, 43)))
 	{
 		// CRLF as per RFC3912
-		fputs($fsk, "$ip\r\n");
+		fputs($fsk, "z $ip\r\n");
 		while (!feof($fsk))
 		{
 			$ipwhois .= fgets($fsk, 1024);