diff --git a/core/modules/rest/src/Entity/RestResourceConfig.php b/core/modules/rest/src/Entity/RestResourceConfig.php
index a31a1a4..fa28292 100644
--- a/core/modules/rest/src/Entity/RestResourceConfig.php
+++ b/core/modules/rest/src/Entity/RestResourceConfig.php
@@ -3,6 +3,7 @@
 namespace Drupal\rest\Entity;
 
 use Drupal\Core\Config\Entity\ConfigEntityBase;
+use Drupal\Core\Entity\EntityStorageInterface;
 use Drupal\Core\Plugin\DefaultSingleLazyPluginCollection;
 use Drupal\rest\RestResourceConfigInterface;
 
@@ -263,4 +264,13 @@ protected function normalizeRestMethod($method) {
     return $normalised_method;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function postSave(EntityStorageInterface $storage, $update = TRUE) {
+    parent::postSave($storage, $update);
+
+    \Drupal::service('router.builder')->setRebuildNeeded();
+  }
+
 }
diff --git a/core/modules/rest/src/Tests/RESTTestBase.php b/core/modules/rest/src/Tests/RESTTestBase.php
index b939bae..13327cb 100644
--- a/core/modules/rest/src/Tests/RESTTestBase.php
+++ b/core/modules/rest/src/Tests/RESTTestBase.php
@@ -418,8 +418,7 @@ protected function enableService($resource_type, $method = 'GET', $format = NULL
    * Rebuilds routing caches.
    */
   protected function rebuildCache() {
-    // Rebuild routing cache, so that the REST API paths are available.
-    $this->container->get('router.builder')->rebuild();
+    $this->container->get('router.builder')->rebuildIfNeeded();
   }
 
   /**