diff --git a/classes/local/utils.php b/classes/local/utils.php
index 34558bb..2cc4dc4 100644
--- a/classes/local/utils.php
+++ b/classes/local/utils.php
@@ -344,8 +344,8 @@ public static function is_private_ipv4_address($address) {
      * if no clients connected.
      */
     public static function get_connected_ip_adresses($interface) {
-        $iwoutput = shell_exec('iw dev ' . $interface . ' station dump') || '';
-        $arpoutput = shell_exec('arp -ai ' . $interface) || '';
+        $iwoutput = shell_exec('iw dev ' . $interface . ' station dump') ?: '';
+        $arpoutput = shell_exec('arp -ai ' . $interface) ?: '';
 
         // Extract MAC and IP addresses.
         preg_match_all('/Station\s+([a-fA-F0-9:]+)/', $iwoutput, $iwmatches);