diff --git a/libraries/classes/Server/Privileges.php b/libraries/classes/Server/Privileges.php
index 0b4d32e313..e76cc4955d 100644
--- a/libraries/classes/Server/Privileges.php
+++ b/libraries/classes/Server/Privileges.php
@@ -2560,7 +2560,8 @@ class Privileges
                 $_POST['old_username'] . '' . $_POST['old_hostname'],
             ];
         } else {
-            $selected_usr = $_POST['selected_usr'];
+            // null happens when no user was selected
+            $selected_usr = $_POST['selected_usr'] ?? null;
             $queries = [];
         }