diff --git a/core/modules/rest/src/Tests/RESTTestBase.php b/core/modules/rest/src/Tests/RESTTestBase.php
index 933187e..ebddc8a 100644
--- a/core/modules/rest/src/Tests/RESTTestBase.php
+++ b/core/modules/rest/src/Tests/RESTTestBase.php
@@ -263,7 +263,7 @@ protected function entityValues($entity_type) {
   protected function enableService($resource_type, $method = 'GET', $format = NULL, $auth = NULL) {
     // Enable REST API for this entity type.
     $config = $this->config('rest.settings');
-    $settings = $config->get('resources');
+    $settings = $resource_type ? $config->get('resources') : [];
 
     if ($resource_type) {
       if ($format == NULL) {