diff --git a/src/Form/QuickTabsInstanceDuplicateForm.php b/src/Form/QuickTabsInstanceDuplicateForm.php
index f78cd5a963a7843edc3c5d7ed8975bb020b11b5d..8e43c8a4f213d0ebdde377d40552044727015ee0 100644
--- a/src/Form/QuickTabsInstanceDuplicateForm.php
+++ b/src/Form/QuickTabsInstanceDuplicateForm.php
@@ -38,7 +38,7 @@ class QuickTabsInstanceDuplicateForm extends EntityForm {
       '#maxlength' => 32,
       '#default_value' => '',
       '#machine_name' => [
-        'exists' => 'quicktabs_machine_name_exists',
+        'exists' => 'Drupal\quicktabs\Entity\QuickTabsInstance::getQuickTabsInstance',
       ],
       '#description' => $this->t('A unique machine-readable name for this QuickTabs instance. It must only contain lowercase letters, numbers, and underscores. The machine name will be used internally by QuickTabs and will be used in the CSS ID of your QuickTabs block.'),
       '#weight' => -8,