diff --git a/core/tests/Drupal/Tests/Core/Entity/EntityManagerTest.php b/core/tests/Drupal/Tests/Core/Entity/EntityManagerTest.php
index 1c260a3..5b3a7e1 100644
--- a/core/tests/Drupal/Tests/Core/Entity/EntityManagerTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/EntityManagerTest.php
@@ -695,6 +695,10 @@ protected function setUpEntityWithFieldDefinition($custom_invoke_all = FALSE, $f
     $entity_type->expects($this->any())
       ->method('getKeys')
       ->will($this->returnValue(array()));
+    $entity_type->expects($this->any())
+      ->method('isSubclassOf')
+      ->with($this->equalTo('\Drupal\Core\Entity\ContentEntityInterface'))
+      ->will($this->returnValue(TRUE));
     $field_definition = $this->getMockBuilder('Drupal\Core\Field\FieldDefinition')
       ->disableOriginalConstructor()
       ->getMock();