diff --git a/core/lib/Drupal/Core/Entity/EntityDisplayBase.php b/core/lib/Drupal/Core/Entity/EntityDisplayBase.php
index ca17e64..8c44a1e 100644
--- a/core/lib/Drupal/Core/Entity/EntityDisplayBase.php
+++ b/core/lib/Drupal/Core/Entity/EntityDisplayBase.php
@@ -128,7 +128,7 @@ public function __construct(array $values, $entity_type) {
       throw new \InvalidArgumentException('Missing required properties for an EntityDisplay entity.');
     }
 
-    if (!$this->entityManager()->getDefinition($values['targetEntityType'])->isSubclassOf('\Drupal\Core\Entity\FieldableEntityInterface')) {
+    if (!$this->entityManager()->getDefinition($values['targetEntityType']) instanceof ContentEntityTypeInterface) {
       throw new \InvalidArgumentException('EntityDisplay entities can only handle fieldable entity types.');
     }
 
diff --git a/core/lib/Drupal/Core/Entity/EntityManager.php b/core/lib/Drupal/Core/Entity/EntityManager.php
index fcba978..60a3ef7 100644
--- a/core/lib/Drupal/Core/Entity/EntityManager.php
+++ b/core/lib/Drupal/Core/Entity/EntityManager.php
@@ -406,7 +406,7 @@ protected function buildBaseFieldDefinitions($entity_type_id) {
     $keys = array_filter($entity_type->getKeys());
 
     // Fail with an exception for non-fieldable entity types.
-    if (!$entity_type->isSubclassOf('\Drupal\Core\Entity\FieldableEntityInterface')) {
+    if (!($entity_type instanceof ContentEntityTypeInterface)) {
       throw new \LogicException(SafeMarkup::format('Getting the base fields is not supported for entity type @type.', array('@type' => $entity_type->getLabel())));
     }
 
@@ -644,7 +644,7 @@ public function getFieldMap() {
       else {
         // Rebuild the definitions and put it into the cache.
         foreach ($this->getDefinitions() as $entity_type_id => $entity_type) {
-          if ($entity_type->isSubclassOf('\Drupal\Core\Entity\FieldableEntityInterface')) {
+          if ($entity_type instanceof ContentEntityTypeInterface) {
             foreach ($this->getBundleInfo($entity_type_id) as $bundle => $bundle_info) {
               foreach ($this->getFieldDefinitions($entity_type_id, $bundle) as $field_name => $field_definition) {
                 $this->fieldMap[$entity_type_id][$field_name]['type'] = $field_definition->getType();
@@ -1087,7 +1087,7 @@ public function onEntityTypeCreate(EntityTypeInterface $entity_type) {
     $this->eventDispatcher->dispatch(EntityTypeEvents::CREATE, new EntityTypeEvent($entity_type));
 
     $this->setLastInstalledDefinition($entity_type);
-    if ($entity_type->isSubclassOf('\Drupal\Core\Entity\FieldableEntityInterface')) {
+    if ($entity_type instanceof ContentEntityTypeInterface) {
       $this->setLastInstalledFieldStorageDefinitions($entity_type_id, $this->getFieldStorageDefinitions($entity_type_id));
     }
   }
diff --git a/core/lib/Drupal/Core/Entity/EntityType.php b/core/lib/Drupal/Core/Entity/EntityType.php
index e121d75..560a624 100644
--- a/core/lib/Drupal/Core/Entity/EntityType.php
+++ b/core/lib/Drupal/Core/Entity/EntityType.php
@@ -270,7 +270,7 @@ public function __construct($definition) {
 
     // Automatically add the EntityChanged constraint if the entity type tracks
     // the changed time.
-    if ($this->isSubclassOf('Drupal\Core\Entity\EntityChangedInterface') ) {
+    if (is_subclass_of($this->getClass(), 'Drupal\Core\Entity\EntityChangedInterface')) {
       $this->addConstraint('EntityChanged');
     }
 
diff --git a/core/lib/Drupal/Core/Entity/Plugin/EntityReferenceSelection/SelectionBase.php b/core/lib/Drupal/Core/Entity/Plugin/EntityReferenceSelection/SelectionBase.php
index cb8c7d6..98146ab 100644
--- a/core/lib/Drupal/Core/Entity/Plugin/EntityReferenceSelection/SelectionBase.php
+++ b/core/lib/Drupal/Core/Entity/Plugin/EntityReferenceSelection/SelectionBase.php
@@ -10,6 +10,7 @@
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Database\Query\AlterableInterface;
 use Drupal\Core\Database\Query\SelectInterface;
+use Drupal\Core\Entity\ContentEntityTypeInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\Form\FormStateInterface;
@@ -142,7 +143,7 @@ public function buildConfigurationForm(array $form, FormStateInterface $form_sta
       );
     }
 
-    if ($entity_type->isSubclassOf('\Drupal\Core\Entity\FieldableEntityInterface')) {
+    if ($entity_type instanceof ContentEntityTypeInterface) {
       $fields = array();
       foreach (array_keys($bundles) as $bundle) {
         $bundle_fields = array_filter($this->entityManager->getFieldDefinitions($entity_type_id, $bundle), function ($field_definition) {
diff --git a/core/lib/Drupal/Core/Field/FieldModuleUninstallValidator.php b/core/lib/Drupal/Core/Field/FieldModuleUninstallValidator.php
index b54579c..74e449c 100644
--- a/core/lib/Drupal/Core/Field/FieldModuleUninstallValidator.php
+++ b/core/lib/Drupal/Core/Field/FieldModuleUninstallValidator.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Field;
 
+use Drupal\Core\Entity\ContentEntityTypeInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\Core\Entity\FieldableEntityStorageInterface;
 use Drupal\Core\Extension\ModuleUninstallValidatorInterface;
@@ -48,7 +49,7 @@ public function validate($module_name) {
         // We skip entity types defined by the module as there must be no
         // content to be able to uninstall them anyway.
         // See \Drupal\Core\Entity\ContentUninstallValidator.
-        if ($entity_type->getProvider() != $module_name && $entity_type->isSubclassOf('\Drupal\Core\Entity\FieldableEntityInterface')) {
+        if ($entity_type->getProvider() != $module_name && $entity_type instanceof ContentEntityTypeInterface) {
           foreach ($this->entityManager->getFieldStorageDefinitions($entity_type_id) as $storage_definition) {
             if ($storage_definition->getProvider() == $module_name) {
               $storage = $this->entityManager->getStorage($entity_type_id);
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
index ca54aa8..cc90a3f 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
+use Drupal\Core\Entity\ContentEntityTypeInterface;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityTypeInterface;
 use Drupal\Core\Entity\TypedData\EntityDataDefinition;
@@ -72,7 +73,7 @@ public static function propertyDefinitions(FieldStorageDefinitionInterface $fiel
     $settings = $field_definition->getSettings();
     $target_type_info = \Drupal::entityManager()->getDefinition($settings['target_type']);
 
-    if ($target_type_info->isSubclassOf('\Drupal\Core\Entity\FieldableEntityInterface')) {
+    if ($target_type_info instanceof ContentEntityTypeInterface) {
       // @todo: Lookup the entity type's ID data type and use it here.
       // https://drupal.org/node/2107249
       $target_id_definition = DataDefinition::create('integer')
@@ -120,7 +121,7 @@ public static function schema(FieldStorageDefinitionInterface $field_definition)
     $target_type = $field_definition->getSetting('target_type');
     $target_type_info = \Drupal::entityManager()->getDefinition($target_type);
 
-    if ($target_type_info->isSubclassOf('\Drupal\Core\Entity\FieldableEntityInterface')) {
+    if ($target_type_info instanceof ContentEntityTypeInterface) {
       $columns = array(
         'target_id' => array(
           'description' => 'The ID of the target entity.',
diff --git a/core/lib/Drupal/Core/ParamConverter/AdminPathConfigEntityConverter.php b/core/lib/Drupal/Core/ParamConverter/AdminPathConfigEntityConverter.php
index ec09f68..fbdaa3c 100644
--- a/core/lib/Drupal/Core/ParamConverter/AdminPathConfigEntityConverter.php
+++ b/core/lib/Drupal/Core/ParamConverter/AdminPathConfigEntityConverter.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\ParamConverter;
 
+use Drupal\Core\Config\Entity\ConfigEntityTypeInterface;
 use Drupal\Core\Routing\AdminContext;
 use Symfony\Component\Routing\Route;
 use Drupal\Core\Config\ConfigFactoryInterface;
@@ -71,7 +72,7 @@ public function convert($value, $definition, $name, array $defaults) {
     // entity types will have performed this check in self::applies().
     if (strpos($definition['type'], 'entity:{') === 0) {
       $entity_type = $this->entityManager->getDefinition($entity_type_id);
-      if (!$entity_type->isSubclassOf('\Drupal\Core\Config\Entity\ConfigEntityInterface')) {
+      if (!$entity_type instanceof ConfigEntityTypeInterface) {
         return parent::convert($value, $definition, $name, $defaults);
       }
     }
@@ -99,7 +100,7 @@ public function applies($definition, $name, Route $route) {
       // As we only want to override EntityConverter for ConfigEntities, find
       // out whether the current entity is a ConfigEntity.
       $entity_type = $this->entityManager->getDefinition($entity_type_id);
-      if ($entity_type->isSubclassOf('\Drupal\Core\Config\Entity\ConfigEntityInterface')) {
+      if ($entity_type instanceof ConfigEntityTypeInterface) {
         return $this->adminContext->isAdminRoute($route);
       }
     }
diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index debc2d3..f06d608 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -14,6 +14,7 @@
 use Drupal\comment\Entity\Comment;
 use Drupal\comment\CommentManagerInterface;
 use Drupal\comment\Entity\CommentType;
+use Drupal\Core\Entity\ContentEntityTypeInterface;
 use Drupal\Core\Entity\FieldableEntityInterface;
 use Drupal\comment\Plugin\Field\FieldType\CommentItemInterface;
 use Drupal\Component\Utility\SafeMarkup;
@@ -311,7 +312,7 @@ function comment_form_field_storage_config_edit_form_alter(&$form, FormStateInte
  */
 function comment_entity_storage_load($entities, $entity_type) {
   // Comments can only be attached to content entities, so skip others.
-  if (!\Drupal::entityManager()->getDefinition($entity_type)->isSubclassOf('Drupal\Core\Entity\FieldableEntityInterface')) {
+  if (!\Drupal::entityManager()->getDefinition($entity_type) instanceof ContentEntityTypeInterface) {
     return;
   }
   if (!\Drupal::service('comment.manager')->getFields($entity_type)) {
diff --git a/core/modules/comment/comment.views.inc b/core/modules/comment/comment.views.inc
index 5e31876..69a1cec 100644
--- a/core/modules/comment/comment.views.inc
+++ b/core/modules/comment/comment.views.inc
@@ -4,6 +4,7 @@
  * @file
  * Provide views data for comment.module.
  */
+use Drupal\Core\Entity\ContentEntityTypeInterface;
 
 /**
  * Implements hook_views_data_alter().
@@ -22,7 +23,7 @@ function comment_views_data_alter(&$data) {
 
   // Provide a integration for each entity type except comment.
   foreach (\Drupal::entityManager()->getDefinitions() as $entity_type_id => $entity_type) {
-    if ($entity_type_id == 'comment' || !$entity_type->isSubclassOf('\Drupal\Core\Entity\ContentEntityInterface') || !$entity_type->getBaseTable()) {
+    if ($entity_type_id == 'comment' || !$entity_type instanceof ContentEntityTypeInterface || !$entity_type->getBaseTable()) {
       continue;
     }
     $fields = \Drupal::service('comment.manager')->getFields($entity_type_id);
diff --git a/core/modules/comment/src/CommentManager.php b/core/modules/comment/src/CommentManager.php
index 45705a2..46d2572 100644
--- a/core/modules/comment/src/CommentManager.php
+++ b/core/modules/comment/src/CommentManager.php
@@ -10,6 +10,7 @@
 use Drupal\comment\Plugin\Field\FieldType\CommentItemInterface;
 use Drupal\Component\Utility\Unicode;
 use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\Entity\ContentEntityTypeInterface;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\Core\Entity\Query\QueryFactory;
@@ -105,7 +106,7 @@ public function __construct(EntityManagerInterface $entity_manager, QueryFactory
    */
   public function getFields($entity_type_id) {
     $entity_type = $this->entityManager->getDefinition($entity_type_id);
-    if (!$entity_type->isSubclassOf('\Drupal\Core\Entity\FieldableEntityInterface')) {
+    if (!$entity_type instanceof ContentEntityTypeInterface) {
       return array();
     }
 
diff --git a/core/modules/comment/src/CommentViewsData.php b/core/modules/comment/src/CommentViewsData.php
index e853a58..4b0bdd6 100644
--- a/core/modules/comment/src/CommentViewsData.php
+++ b/core/modules/comment/src/CommentViewsData.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\comment;
 
+use Drupal\Core\Entity\ContentEntityTypeInterface;
 use Drupal\views\EntityViewsData;
 
 /**
@@ -159,7 +160,7 @@ public function getViewsData() {
 
     // Provide a relationship for each entity type except comment.
     foreach ($entities_types as $type => $entity_type) {
-      if ($type == 'comment' || !$entity_type->isSubclassOf('\Drupal\Core\Entity\ContentEntityInterface') || !$entity_type->getBaseTable()) {
+      if ($type == 'comment' || !$entity_type instanceof ContentEntityTypeInterface || !$entity_type->getBaseTable()) {
         continue;
       }
       if ($fields = \Drupal::service('comment.manager')->getFields($type)) {
@@ -211,7 +212,7 @@ public function getViewsData() {
 
     // Provide a relationship for each entity type except comment.
     foreach ($entities_types as $type => $entity_type) {
-      if ($type == 'comment' || !$entity_type->isSubclassOf('\Drupal\Core\Entity\ContentEntityInterface') || !$entity_type->getBaseTable()) {
+      if ($type == 'comment' || !$entity_type instanceof ContentEntityTypeInterface || !$entity_type->getBaseTable()) {
         continue;
       }
       // This relationship does not use the 'field id' column, if the entity has
diff --git a/core/modules/config/src/Form/ConfigSingleExportForm.php b/core/modules/config/src/Form/ConfigSingleExportForm.php
index c95f0d8..0c2522f 100644
--- a/core/modules/config/src/Form/ConfigSingleExportForm.php
+++ b/core/modules/config/src/Form/ConfigSingleExportForm.php
@@ -8,6 +8,7 @@
 namespace Drupal\config\Form;
 
 use Drupal\Component\Serialization\Yaml;
+use Drupal\Core\Config\Entity\ConfigEntityTypeInterface;
 use Drupal\Core\Config\StorageInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\Core\Entity\EntityTypeInterface;
@@ -77,7 +78,7 @@ public function getFormID() {
    */
   public function buildForm(array $form, FormStateInterface $form_state, $config_type = NULL, $config_name = NULL) {
     foreach ($this->entityManager->getDefinitions() as $entity_type => $definition) {
-      if ($definition->isSubclassOf('Drupal\Core\Config\Entity\ConfigEntityInterface')) {
+      if ($definition instanceof ConfigEntityTypeInterface) {
         $this->definitions[$entity_type] = $definition;
       }
     }
diff --git a/core/modules/config/src/Form/ConfigSingleImportForm.php b/core/modules/config/src/Form/ConfigSingleImportForm.php
index 84c19db..b12da1d 100644
--- a/core/modules/config/src/Form/ConfigSingleImportForm.php
+++ b/core/modules/config/src/Form/ConfigSingleImportForm.php
@@ -8,6 +8,7 @@
 namespace Drupal\config\Form;
 
 use Drupal\Component\Serialization\Yaml;
+use Drupal\Core\Config\Entity\ConfigEntityTypeInterface;
 use Drupal\Core\Config\StorageInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\Core\Form\ConfirmFormBase;
@@ -123,7 +124,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
 
     $entity_types = array();
     foreach ($this->entityManager->getDefinitions() as $entity_type => $definition) {
-      if ($definition->isSubclassOf('Drupal\Core\Config\Entity\ConfigEntityInterface')) {
+      if ($definition instanceof ConfigEntityTypeInterface) {
         $entity_types[$entity_type] = $definition->getLabel();
       }
     }
diff --git a/core/modules/config_translation/config_translation.module b/core/modules/config_translation/config_translation.module
index ea4e532..2762015 100644
--- a/core/modules/config_translation/config_translation.module
+++ b/core/modules/config_translation/config_translation.module
@@ -6,6 +6,7 @@
  */
 
 use Drupal\config_translation\Plugin\Derivative\ConfigTranslationLocalTasks;
+use Drupal\Core\Config\Entity\ConfigEntityTypeInterface;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Routing\RouteMatchInterface;
 use Drupal\field\FieldConfigInterface;
@@ -77,7 +78,7 @@ function config_translation_themes_uninstalled() {
 function config_translation_entity_type_alter(array &$entity_types) {
   /** @var $entity_types \Drupal\Core\Entity\EntityTypeInterface[] */
   foreach ($entity_types as $entity_type_id => $entity_type) {
-    if ($entity_type->isSubclassOf('Drupal\Core\Config\Entity\ConfigEntityInterface')) {
+    if ($entity_type instanceof ConfigEntityTypeInterface) {
       if ($entity_type_id == 'block') {
         $class = 'Drupal\config_translation\Controller\ConfigTranslationBlockListBuilder';
       }
@@ -129,7 +130,7 @@ function config_translation_config_translation_info(&$info) {
     // Determine base path for entities automatically if provided via the
     // configuration entity.
     if (
-      !$entity_type->isSubclassOf('Drupal\Core\Config\Entity\ConfigEntityInterface') ||
+      !$entity_type instanceof ConfigEntityTypeInterface ||
       !$entity_type->hasLinkTemplate('edit-form')
     ) {
       // Do not record this entity mapper if the entity type does not
@@ -158,7 +159,7 @@ function config_translation_config_translation_info(&$info) {
 function config_translation_entity_operation(EntityInterface $entity) {
   $operations = array();
   $entity_type = $entity->getEntityType();
-  if ($entity_type->isSubclassOf('Drupal\Core\Config\Entity\ConfigEntityInterface') &&
+  if ($entity_type instanceof ConfigEntityTypeInterface &&
     $entity->hasLinkTemplate('config-translation-overview') &&
     \Drupal::currentUser()->hasPermission('translate configuration')) {
 
diff --git a/core/modules/rest/src/LinkManager/TypeLinkManager.php b/core/modules/rest/src/LinkManager/TypeLinkManager.php
index 4160b2b..4f1cb23 100644
--- a/core/modules/rest/src/LinkManager/TypeLinkManager.php
+++ b/core/modules/rest/src/LinkManager/TypeLinkManager.php
@@ -9,6 +9,7 @@
 
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Cache\CacheBackendInterface;
+use Drupal\Core\Entity\ContentEntityTypeInterface;
 use Drupal\Core\Utility\UnroutedUrlAssemblerInterface;
 
 class TypeLinkManager implements TypeLinkManagerInterface {
@@ -96,7 +97,7 @@ protected function writeCache() {
     foreach (entity_get_bundles() as $entity_type_id => $bundles) {
       // Only content entities are supported currently.
       // @todo Consider supporting config entities.
-      if ($entity_types[$entity_type_id]->isSubclassOf('\Drupal\Core\Config\Entity\ConfigEntityInterface')) {
+      if (!($entity_types[$entity_type_id] instanceof ContentEntityTypeInterface)) {
         continue;
       }
       foreach ($bundles as $bundle => $bundle_info) {