diff --git a/core/modules/image/tests/src/Kernel/ImageItemTest.php b/core/modules/image/tests/src/Kernel/ImageItemTest.php
index 1c63a22..dea4534 100644
--- a/core/modules/image/tests/src/Kernel/ImageItemTest.php
+++ b/core/modules/image/tests/src/Kernel/ImageItemTest.php
@@ -53,6 +53,9 @@ protected function setUp() {
       'entity_type' => 'entity_test',
       'field_name' => 'image_test',
       'bundle' => 'entity_test',
+      'settings' => [
+        'file_extensions' => 'jpg',
+      ],
     ])->save();
     file_unmanaged_copy(\Drupal::root() . '/core/misc/druplicon.png', 'public://example.jpg');
     $this->image = File::create([
@@ -123,6 +126,7 @@ public function testImageItem() {
     $entity = EntityTest::create();
     $entity->image_test->generateSampleItems();
     $this->entityValidateAndSave($entity);
+    $this->assertEqual($entity->image_test->entity->get('filemime')->value, 'image/jpeg');
   }
 
 }