diff --git a/core/modules/rest/tests/src/Functional/EntityResource/ConfigTest/ConfigTestResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/ConfigTest/ConfigTestResourceTestBase.php
index b89a2718dc..c34e8e2b1a 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/ConfigTest/ConfigTestResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/ConfigTest/ConfigTestResourceTestBase.php
@@ -32,7 +32,11 @@
   /**
    * {@inheritdoc}
    */
-  protected static $firstCreatedEntityId = 'llama';
+  protected static $firstCreatedEntityId = 'llama1';
+
+  public function setUp() {
+    parent::setUp();
+  }
 
   /**
    * {@inheritdoc}
@@ -55,7 +59,7 @@ protected function setUpAuthorization($method) {
    */
   protected function createEntity() {
     $config_test = ConfigTest::create([
-      'id' => 'llama',
+      'id' => 'llama' . (string) $this->counter,
       'label' => 'Llama',
     ]);
     $config_test->save();
@@ -69,7 +73,7 @@ protected function createEntity() {
   protected function getExpectedNormalizedEntity() {
     $normalization = [
       'uuid' => $this->entity->uuid(),
-      'id' => 'llama',
+      'id' => 'llama' . (string) $this->counter,
       'weight' => 0,
       'langcode' => 'en',
       'status' => TRUE,
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
index 6345b0b185..6fd975a3a5 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
@@ -879,7 +879,7 @@ public function testPost() {
     foreach ($this->getNormalizedPostEntity() as $field_name => $field_normalization) {
       // Some top-level keys in the normalization may not be fields on the
       // entity (for example '_links' and '_embedded' in the HAL normalization).
-      if ($created_entity->hasField($field_name)) {
+      if ($created_entity instanceof  FieldableEntityInterface && $created_entity->hasField($field_name)) {
         // Subset, not same, because we can e.g. send just the target_id for the
         // bundle in a POST request; the response will include more properties.
         $this->assertArraySubset(static::castToString($field_normalization), $created_entity->get($field_name)->getValue(), TRUE);