diff --git a/core/modules/aggregator/aggregator.install b/core/modules/aggregator/aggregator.install
index e236628..a423636 100644
--- a/core/modules/aggregator/aggregator.install
+++ b/core/modules/aggregator/aggregator.install
@@ -37,3 +37,16 @@ function aggregator_update_8001() {
 /**
  * @} End of "addtogroup updates-8.0.0-rc".
  */
+
+/**
+ * Promote 'guid' field to uuid entity key.
+ */
+function aggregator_update_8002() {
+  $manager = \Drupal::entityDefinitionUpdateManager();
+  $entity_type = $manager->getEntityType('aggregator_item');
+  $entity_keys = $entity_type->getKeys();
+  $entity_keys['uuid'] = 'guid';
+  $entity_type->set('entity_keys', $entity_keys);
+  $manager->updateEntityType($entity_type);
+  $manager->updateFieldStorageDefinition($manager->getFieldStorageDefinition('guid', 'aggregator_item'));
+}
diff --git a/core/modules/aggregator/src/Entity/Item.php b/core/modules/aggregator/src/Entity/Item.php
index 4c6d104..c5543e6 100644
--- a/core/modules/aggregator/src/Entity/Item.php
+++ b/core/modules/aggregator/src/Entity/Item.php
@@ -36,6 +36,7 @@
  *     "id" = "iid",
  *     "label" = "title",
  *     "langcode" = "langcode",
+ *     "uuid" = "guid",
  *   }
  * )
  */
@@ -109,11 +110,10 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
       ))
       ->setDisplayConfigurable('view', TRUE);
 
-    // @todo Convert to a real UUID field in
-    //   https://www.drupal.org/node/2149851.
-    $fields['guid'] = BaseFieldDefinition::create('string_long')
+    $fields['guid'] = BaseFieldDefinition::create('uuid')
       ->setLabel(t('GUID'))
-      ->setDescription(t('Unique identifier for the feed item.'));
+      ->setDescription(t('Unique identifier for the feed item.'))
+      ->setReadOnly(TRUE);
 
     return $fields;
   }
diff --git a/core/modules/aggregator/src/Tests/Views/IntegrationTest.php b/core/modules/aggregator/src/Tests/Views/IntegrationTest.php
index 98598c4..8b2e559 100644
--- a/core/modules/aggregator/src/Tests/Views/IntegrationTest.php
+++ b/core/modules/aggregator/src/Tests/Views/IntegrationTest.php
@@ -91,7 +91,7 @@ public function testAggregatorItemView() {
       // Add a image to ensure that the sanitizing can be tested below.
       $values['author'] = $this->randomMachineName() . '<img src="http://example.com/example.png" \>"';
       $values['link'] = 'https://www.drupal.org/node/' . mt_rand(1000, 10000);
-      $values['guid'] = $this->randomString();
+      $values['guid'] = 'guid-' . $i;
 
       $aggregator_item = $this->itemStorage->create($values);
       $aggregator_item->save();
@@ -134,6 +134,16 @@ public function testAggregatorItemView() {
       });
       $this->assertEqual($output, $expected_description, 'Ensure the author got filtered');
     }
+
+    // Test if an aggregator item can be rendered in the header.
+    $view = Views::getView('test_aggregator_items');
+    $view->setDisplay('default');
+    $this->executeView($view);
+    $output = $view->render();
+    $output = \Drupal::service('renderer')->renderRoot($output);
+    $this->setRawContent($output);
+    $header = $this->cssSelect('header h3 a');
+    $this->assertEqual(trim($header[0]), $expected[1]['title']);
   }
 
 }
diff --git a/core/modules/aggregator/tests/modules/aggregator_test_views/test_views/views.view.test_aggregator_items.yml b/core/modules/aggregator/tests/modules/aggregator_test_views/test_views/views.view.test_aggregator_items.yml
index db7b203..6776ef2 100644
--- a/core/modules/aggregator/tests/modules/aggregator_test_views/test_views/views.view.test_aggregator_items.yml
+++ b/core/modules/aggregator/tests/modules/aggregator_test_views/test_views/views.view.test_aggregator_items.yml
@@ -182,6 +182,20 @@ display:
           entity_type: aggregator_item
           entity_field: iid
           order: 'ASC'
+      header:
+        entity_aggregator_item:
+          id: entity_aggregator_item
+          table: views
+          field: entity_aggregator_item
+          relationship: none
+          group_type: group
+          admin_label: ''
+          empty: false
+          tokenize: true
+          target: guid-1
+          view_mode: default
+          bypass_access: true
+          plugin_id: entity
   feed_1:
     display_plugin: feed
     id: feed_1