diff --git a/lib/moodlelib.php b/lib/moodlelib.php
index cf2e9fdc2e4..dd2311862a1 100644
--- a/lib/moodlelib.php
+++ b/lib/moodlelib.php
@@ -9207,7 +9207,7 @@ function getremoteaddr($default='0.0.0.0') {
 
             $forwardedaddresses = array_filter($forwardedaddresses, function($ip) {
                 global $CFG;
-                return !\core\ip_utils::is_ip_in_subnet_list($ip, $CFG->reverseproxyignore, ',');
+                return !\core\ip_utils::is_ip_in_subnet_list($ip, $CFG->reverseproxyignore ?? '', ',');
             });
 
             // Multiple proxies can append values to this header including an