diff --git a/core/lib/Drupal/Core/Entity/EntityDisplayBase.php b/core/lib/Drupal/Core/Entity/EntityDisplayBase.php
index 4de891a..a518209 100644
--- a/core/lib/Drupal/Core/Entity/EntityDisplayBase.php
+++ b/core/lib/Drupal/Core/Entity/EntityDisplayBase.php
@@ -122,7 +122,7 @@ 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/EntityType.php b/core/lib/Drupal/Core/Entity/EntityType.php
index a63415b..fa1c6d0 100644
--- a/core/lib/Drupal/Core/Entity/EntityType.php
+++ b/core/lib/Drupal/Core/Entity/EntityType.php
@@ -14,6 +14,11 @@
  */
 class EntityType implements EntityTypeInterface {
 
+  /*
+   * Defines EntityChangedInterface constant for internal usage
+   */
+  const ENTITY_TYPE_ENTITY_CHANGED_INTERFACE = 'Drupal\Core\Entity\EntityChangedInterface';
+  
   use StringTranslationTrait;
 
   /**
@@ -301,7 +306,7 @@ 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(), self::ENTITY_TYPE_ENTITY_CHANGED_INTERFACE)) {
       $this->addConstraint('EntityChanged');
     }
 
diff --git a/core/lib/Drupal/Core/Entity/EntityTypeInterface.php b/core/lib/Drupal/Core/Entity/EntityTypeInterface.php
index 398347f..7011f28 100644
--- a/core/lib/Drupal/Core/Entity/EntityTypeInterface.php
+++ b/core/lib/Drupal/Core/Entity/EntityTypeInterface.php
@@ -359,6 +359,8 @@ public function setAccessClass($class);
    *
    * @return bool
    *   TRUE if the entity type is a subclass of the class or interface.
+   *
+   * @deprecated in Drupal 8.0.x-dev, will be removed before Drupal 9.0.0
    */
   public function isSubclassOf($class);
 
diff --git a/core/lib/Drupal/Core/Field/FieldModuleUninstallValidator.php b/core/lib/Drupal/Core/Field/FieldModuleUninstallValidator.php
index d1adaa9..dc75fb0 100644
--- a/core/lib/Drupal/Core/Field/FieldModuleUninstallValidator.php
+++ b/core/lib/Drupal/Core/Field/FieldModuleUninstallValidator.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\Core\Field;
 
+use Drupal\Core\Entity\ContentEntityTypeInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\Core\Entity\FieldableEntityStorageInterface;
 use Drupal\Core\Extension\ModuleUninstallValidatorInterface;
@@ -43,7 +44,7 @@ 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 e8832f3..f2a3145 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
@@ -4,6 +4,7 @@
 
 use Drupal\Component\Utility\Html;
 use Drupal\Component\Utility\NestedArray;
+use Drupal\Core\Entity\ContentEntityTypeInterface;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityTypeInterface;
 use Drupal\Core\Entity\TypedData\EntityDataDefinition;
@@ -66,7 +67,7 @@ public static function propertyDefinitions(FieldStorageDefinitionInterface $fiel
     $target_type_info = \Drupal::entityManager()->getDefinition($settings['target_type']);
 
     $target_id_data_type = 'string';
-    if ($target_type_info->isSubclassOf('\Drupal\Core\Entity\FieldableEntityInterface')) {
+    if ($target_type_info instanceof ContentEntityTypeInterface) {
       $id_definition = \Drupal::entityManager()->getBaseFieldDefinitions($settings['target_type'])[$target_type_info->getKey('id')];
       if ($id_definition->getType() === 'integer') {
         $target_id_data_type = 'integer';
diff --git a/core/lib/Drupal/Core/ParamConverter/AdminPathConfigEntityConverter.php b/core/lib/Drupal/Core/ParamConverter/AdminPathConfigEntityConverter.php
index 9420e8d..515a9e2 100644
--- a/core/lib/Drupal/Core/ParamConverter/AdminPathConfigEntityConverter.php
+++ b/core/lib/Drupal/Core/ParamConverter/AdminPathConfigEntityConverter.php
@@ -2,6 +2,7 @@
 
 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;
@@ -65,7 +66,7 @@ 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, $defaults);
       }
     }
@@ -93,7 +94,7 @@ public function applies($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.views.inc b/core/modules/comment/comment.views.inc
index 5e31876..6e68c7f 100644
--- a/core/modules/comment/comment.views.inc
+++ b/core/modules/comment/comment.views.inc
@@ -20,16 +20,15 @@ function comment_views_data_alter(&$data) {
     ),
   );
 
-  // Provide a integration for each entity type except comment.
+  // Provide a integration for each entity type with fields 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->getBaseTable()) {
       continue;
     }
-    $fields = \Drupal::service('comment.manager')->getFields($entity_type_id);
-    $base_table = $entity_type->getDataTable() ?: $entity_type->getBaseTable();
-    $args = array('@entity_type' => $entity_type_id);
 
-    if ($fields) {
+    if ($fields = \Drupal::service('comment.manager')->getFields($entity_type_id)) {
+      $base_table = $entity_type->getDataTable() ?: $entity_type->getBaseTable();
+      $args = array('@entity_type' => $entity_type_id);
       $data[$base_table]['comments_link'] = array(
         'field' => array(
           'title' => t('Add comment link'),
diff --git a/core/modules/comment/src/CommentManager.php b/core/modules/comment/src/CommentManager.php
index fcec230..8fdeb4e 100644
--- a/core/modules/comment/src/CommentManager.php
+++ b/core/modules/comment/src/CommentManager.php
@@ -4,6 +4,7 @@
 
 use Drupal\comment\Plugin\Field\FieldType\CommentItemInterface;
 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;
@@ -99,7 +100,8 @@ 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) {
+      // Early return, only content types can carry comment fields.
       return array();
     }
 
diff --git a/core/modules/comment/src/CommentViewsData.php b/core/modules/comment/src/CommentViewsData.php
index 2d9b021..bb92b16 100644
--- a/core/modules/comment/src/CommentViewsData.php
+++ b/core/modules/comment/src/CommentViewsData.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\comment;
 
+use Drupal\Core\Entity\ContentEntityTypeInterface;
 use Drupal\views\EntityViewsData;
 
 /**
@@ -184,7 +185,7 @@ 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)) {
@@ -226,7 +227,7 @@ 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/comment/tests/src/Unit/CommentManagerTest.php b/core/modules/comment/tests/src/Unit/CommentManagerTest.php
index 7fe1c16..1e1494c 100644
--- a/core/modules/comment/tests/src/Unit/CommentManagerTest.php
+++ b/core/modules/comment/tests/src/Unit/CommentManagerTest.php
@@ -22,10 +22,6 @@ public function testGetFields() {
     $entity_type->expects($this->any())
       ->method('getClass')
       ->will($this->returnValue('Node'));
-    $entity_type->expects($this->any())
-      ->method('isSubclassOf')
-      ->with('\Drupal\Core\Entity\FieldableEntityInterface')
-      ->will($this->returnValue(TRUE));
 
     $entity_manager = $this->getMock('Drupal\Core\Entity\EntityManagerInterface');
 
diff --git a/core/modules/config/src/Form/ConfigSingleExportForm.php b/core/modules/config/src/Form/ConfigSingleExportForm.php
index b6bc0e7..2af639a 100644
--- a/core/modules/config/src/Form/ConfigSingleExportForm.php
+++ b/core/modules/config/src/Form/ConfigSingleExportForm.php
@@ -3,6 +3,7 @@
 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;
@@ -73,7 +74,7 @@ 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 09bc6f2..f5272e4 100644
--- a/core/modules/config/src/Form/ConfigSingleImportForm.php
+++ b/core/modules/config/src/Form/ConfigSingleImportForm.php
@@ -9,6 +9,7 @@
 use Drupal\Core\Config\ConfigImporterException;
 use Drupal\Core\Config\ConfigManagerInterface;
 use Drupal\Core\Config\StorageComparer;
+use Drupal\Core\Config\Entity\ConfigEntityTypeInterface;
 use Drupal\Core\Config\StorageInterface;
 use Drupal\Core\Config\TypedConfigManagerInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
@@ -221,7 +222,7 @@ 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 9f0803d..73105c0 100644
--- a/core/modules/config_translation/config_translation.module
+++ b/core/modules/config_translation/config_translation.module
@@ -5,6 +5,7 @@
  * Configuration Translation module.
  */
 
+use Drupal\Core\Config\Entity\ConfigEntityTypeInterface;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Routing\RouteMatchInterface;
 use Drupal\field\FieldConfigInterface;
@@ -75,7 +76,7 @@ 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') {
         $class = 'Drupal\config_translation\Controller\ConfigTranslationBlockListBuilder';
       }
@@ -125,7 +126,7 @@ function config_translation_config_translation_info(&$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 ||
       !$entity_type->hasLinkTemplate('edit-form')
     ) {
       // Do not record this entity mapper if the entity type does not
@@ -154,7 +155,7 @@ function config_translation_config_translation_info(&$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 f767d06..d30388d 100644
--- a/core/modules/rest/src/LinkManager/TypeLinkManager.php
+++ b/core/modules/rest/src/LinkManager/TypeLinkManager.php
@@ -4,6 +4,7 @@
 
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Cache\CacheBackendInterface;
+use Drupal\Core\Entity\ContentEntityTypeInterface;
 use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Symfony\Component\HttpFoundation\RequestStack;
@@ -110,7 +111,7 @@ protected function writeCache($context = array()) {
     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) {