diff --git a/core/modules/jsonapi/tests/src/Functional/ResourceTestBase.php b/core/modules/jsonapi/tests/src/Functional/ResourceTestBase.php
index 626a4c13cc75f7414355bb50f68db3f75fe59e43..17f4e2b809a1e052c67beb2b987ad9f5c18dff8e 100644
--- a/core/modules/jsonapi/tests/src/Functional/ResourceTestBase.php
+++ b/core/modules/jsonapi/tests/src/Functional/ResourceTestBase.php
@@ -428,7 +428,6 @@ protected function getEntityDuplicate(EntityInterface $original, $key) {
     }
     if ($duplicate instanceof ConfigEntityInterface && $id_key = $duplicate->getEntityType()->getKey('id')) {
       $id = $original->id();
-      $id_key = $duplicate->getEntityType()->getKey('id');
       $duplicate->set($id_key, $id . '_' . $key);
     }
     return $duplicate;