diff --git a/lib/adminlib.php b/lib/adminlib.php
index 052a0d47f2f..6d04ea2a076 100644
--- a/lib/adminlib.php
+++ b/lib/adminlib.php
@@ -4050,13 +4050,13 @@ class admin_setting_configduration extends admin_setting {
         $context = (object) [
             'id' => $this->get_id(),
             'name' => $this->get_full_name(),
-            'value' => $data['v'],
+            'value' => $data['v'] ?? '',
             'readonly' => $this->is_readonly(),
             'options' => array_map(function($unit) use ($units, $data, $defaultunit) {
                 return [
                     'value' => $unit,
                     'name' => $units[$unit],
-                    'selected' => ($data['v'] == 0 && $unit == $defaultunit) || $unit == $data['u']
+                    'selected' => isset($data) && (($data['v'] == 0 && $unit == $defaultunit) || $unit == $data['u'])
                 ];
             }, array_keys($units))
         ];