diff --git a/library/includes/functions.php b/library/includes/functions.php
index d254bf9fd..dd4438b44 100644
--- a/library/includes/functions.php
+++ b/library/includes/functions.php
@@ -264,6 +264,11 @@ function auth($type, $forum_id, $ug_data, array $f_access = [], $group_perm = UG
 {
     global $lang, $bf, $datastore;
 
+    // Check for forum existence
+    if (!forum_exists($forum_id)) {
+        return [];
+    }
+
     $is_guest = true;
     $is_admin = false;
     $auth = $auth_fields = $u_access = [];