diff --git a/core/modules/rest/rest.install b/core/modules/rest/rest.install
index 4bca69b..3be359c 100644
--- a/core/modules/rest/rest.install
+++ b/core/modules/rest/rest.install
@@ -5,6 +5,8 @@
  * Install, update and uninstall functions for the rest module.
  */
 
+use Drupal\rest\Entity\RestEndpoint;
+
 /**
  * Implements hook_requirements().
  */
@@ -21,3 +23,20 @@ function rest_requirements($phase) {
   }
   return $requirements;
 }
+
+/**
+ * Install the REST endpoint entity type and convert old settings-based config.
+ */
+function rest_update_8001() {
+  \Drupal::entityDefinitionUpdateManager()->installEntityType(\Drupal::entityTypeManager()->getDefinition('rest_endpoint'));
+  foreach (\Drupal::config('rest.settings')->get('resources') as $key => $resource) {
+    $resource = RestEndpoint::create([
+      'id' => str_replace(':', '__', $key),
+      'configuration' => $resource,
+    ]);
+    $resource->save();
+  }
+  \Drupal::configFactory()->getEditable('rest.settings')
+    ->clear('resources')
+    ->save();
+}
diff --git a/core/modules/rest/src/Entity/RestEndpoint.php b/core/modules/rest/src/Entity/RestEndpoint.php
index cfc96f5..28ee69b 100644
--- a/core/modules/rest/src/Entity/RestEndpoint.php
+++ b/core/modules/rest/src/Entity/RestEndpoint.php
@@ -28,6 +28,11 @@
  *   label_callback = "getLabelFromPlugin",
  *   entity_keys = {
  *     "id" = "id"
+ *   },
+ *   config_export = {
+ *     "id",
+ *     "plugin_id",
+ *     "configuration"
  *   }
  * )
  */
@@ -74,7 +79,8 @@ public function __construct(array $values, $entity_type) {
     $this->logger = \Drupal::service('logger.factory')->get('rest');
     $this->setContainer(\Drupal::getContainer());
     parent::__construct($values, $entity_type);
-    // The config entity id looks like the plugin id but uses _ instead of : because : is not valid for config entities.
+    // The config entity id looks like the plugin id but uses __ instead of :
+    // because : is not valid for config entities.
     if (!isset($this->plugin_id) && isset($this->id)) {
       // Generate plugin_id on first entity creation
       $this->plugin_id = str_replace('__', ':', $this->id);
diff --git a/core/modules/system/src/Tests/Update/UpdatePathTestBase.php b/core/modules/system/src/Tests/Update/UpdatePathTestBase.php
index e5780a1..114b4a0 100644
--- a/core/modules/system/src/Tests/Update/UpdatePathTestBase.php
+++ b/core/modules/system/src/Tests/Update/UpdatePathTestBase.php
@@ -270,7 +270,15 @@ protected function runUpdates() {
     }
 
     // Ensure that the update hooks updated all entity schema.
-    $this->assertFalse(\Drupal::service('entity.definition_update_manager')->needsUpdates(), 'After all updates ran, entity schema is up to date.');
+    $needs_updates = \Drupal::entityDefinitionUpdateManager()->needsUpdates();
+    $this->assertFalse($needs_updates, 'After all updates ran, entity schema is up to date.');
+    if ($needs_updates) {
+      foreach (\Drupal::entityDefinitionUpdateManager()->getChangeSummary() as $entity_type_id => $summary) {
+        foreach ($summary as $message) {
+          $this->fail($message);
+        }
+      }
+    }
   }
 
   /**
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index afa5892..e6b06af 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -1350,7 +1350,11 @@ function system_update_8004() {
   $manager = \Drupal::entityDefinitionUpdateManager();
   foreach (array_keys(\Drupal::entityManager()
     ->getDefinitions()) as $entity_type_id) {
-    $manager->updateEntityType($manager->getEntityType($entity_type_id));
+    // Only update the entity type if it already exists. This condition is
+    // needed in case new entity types are introduced after this update.
+    if ($entity_type = $manager->getEntityType($entity_type_id)) {
+      $manager->updateEntityType($entity_type);
+    }
   }
 }