diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
index 41d9eec849..0fa178daf6 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
@@ -473,12 +473,17 @@ public function testGet() {
     if ($this->entity->getEntityType()->getLinkTemplates()) {
       $this->assertArrayHasKey('Link', $response->getHeaders());
       $link_relation_type_manager = $this->container->get('plugin.manager.link_relation_type');
+      // Filter out definitions that do not have a plugin.
+      // @see \Drupal\rest\Plugin\rest\resource\EntityResource::addLinkHeaders()
+      $link_relations = array_values(array_filter(array_keys($this->entity->getEntityType()->getLinkTemplates()), function ($relation_name) use ($link_relation_type_manager) {
+        return $link_relation_type_manager->hasDefinition($relation_name);
+      }));
       $expected_link_relation_headers = array_map(function ($relation_name) use ($link_relation_type_manager) {
         $link_relation_type = $link_relation_type_manager->createInstance($relation_name);
         return $link_relation_type->isRegistered()
           ? $link_relation_type->getRegisteredName()
           : $link_relation_type->getExtensionUri();
-      }, array_keys($this->entity->getEntityType()->getLinkTemplates()));
+      }, $link_relations);
       $parse_rel_from_link_header = function ($value) use ($link_relation_type_manager) {
         $matches = [];
         if (preg_match('/rel="([^"]+)"/', $value, $matches) === 1) {
diff --git a/core/modules/system/tests/modules/entity_test/entity_test.module b/core/modules/system/tests/modules/entity_test/entity_test.module
index 025cb5fc2f..d595d4a320 100644
--- a/core/modules/system/tests/modules/entity_test/entity_test.module
+++ b/core/modules/system/tests/modules/entity_test/entity_test.module
@@ -71,6 +71,7 @@ function entity_test_entity_types($filter = NULL) {
     $types[] = 'entity_test_base_field_display';
     $types[] = 'entity_test_string_id';
     $types[] = 'entity_test_no_id';
+    $types[] = 'entity_test_mul_with_bundle';
   }
   $types[] = 'entity_test_mulrev';
   $types[] = 'entity_test_mulrev_changed';
@@ -199,7 +200,7 @@ function entity_test_entity_bundle_info() {
   $bundles = [];
   $entity_types = \Drupal::entityManager()->getDefinitions();
   foreach ($entity_types as $entity_type_id => $entity_type) {
-    if ($entity_type->getProvider() == 'entity_test' && $entity_type_id != 'entity_test_with_bundle') {
+    if ($entity_type->getProvider() == 'entity_test' && !in_array($entity_type_id, ['entity_test_with_bundle', 'entity_test_mul_with_bundle'], TRUE)) {
       $bundles[$entity_type_id] = \Drupal::state()->get($entity_type_id . '.bundles') ?: [$entity_type_id => ['label' => 'Entity Test Bundle']];
     }
   }