diff --git a/core/lib/Drupal/Core/Entity/ContentEntityBase.php b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
index 1d69be2..4770eae 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityBase.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
@@ -149,6 +149,13 @@
   protected $validationRequired = FALSE;
 
   /**
+   * Whether to serialize the initialized fields when serializing the entity.
+   *
+   * @var bool
+   */
+  public $serializeFields = FALSE;
+
+  /**
    * {@inheritdoc}
    */
   public function __construct(array $values, $entity_type, $bundle = FALSE, $translations = array()) {
@@ -416,7 +423,8 @@ public function __sleep() {
         $this->values[$name][$langcode] = $field->getValue();
       }
     }
-    $this->fields = array();
+    // Serialize initialized fields only if requested so.
+    $this->fields = $this->serializeFields ? $this->fields : [];
     $this->fieldDefinitions = NULL;
     $this->languages = NULL;
     $this->clearTranslationCache();
@@ -427,6 +435,14 @@ public function __sleep() {
   /**
    * {@inheritdoc}
    */
+  public function __wakeup() {
+    $this->serializeFields = FALSE;
+    parent::__wakeup();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function id() {
     return $this->getEntityKey('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 63bd90d..d31f79a 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
@@ -664,4 +664,16 @@ public static function getPreconfiguredOptions() {
     return $options;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function __sleep() {
+    // If the parent entity is serializing the initialized fields so have to do
+    // the referenced entity as well.
+    if ($this->getEntity()->serializeFields && isset($this->entity)) {
+      $this->entity->serializeFields = TRUE;
+    }
+    return parent::__sleep();
+  }
+
 }
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/EntitySerializationTest.php b/core/tests/Drupal/KernelTests/Core/Entity/EntitySerializationTest.php
new file mode 100644
index 0000000..7711b57
--- /dev/null
+++ b/core/tests/Drupal/KernelTests/Core/Entity/EntitySerializationTest.php
@@ -0,0 +1,185 @@
+<?php
+
+namespace Drupal\KernelTests\Core\Entity;
+
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\field\Tests\EntityReference\EntityReferenceTestTrait;
+
+/**
+ * Tests entity serialization.
+ *
+ * @group Entity
+ */
+class EntitySerializationTest extends EntityKernelTestBase {
+
+  use EntityReferenceTestTrait;
+
+  /**
+   * The entity type used in this test.
+   *
+   * @var string
+   */
+  protected $entityType = 'entity_test';
+
+  /**
+   * The entity type that is being referenced.
+   *
+   * @var string
+   */
+  protected $referencedEntityType = 'entity_test_rev';
+
+  /**
+   * The bundle used in this test.
+   *
+   * @var string
+   */
+  protected $bundle = 'entity_test';
+
+  /**
+   * The name of the entity reference field used in this test.
+   *
+   * @var string
+   */
+  protected $fieldName = 'field_test';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $this->installEntitySchema('entity_test_rev');
+
+    // Create the entity reference fields.
+    $this->createEntityReferenceField(
+      $this->entityType,
+      $this->bundle,
+      $this->fieldName,
+      'Field test',
+      $this->referencedEntityType,
+      'default',
+      array('target_bundles' => array($this->bundle)),
+      FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED
+    );
+
+    $this->createEntityReferenceField(
+      $this->referencedEntityType,
+      $this->bundle,
+      $this->fieldName,
+      'Field test',
+      $this->referencedEntityType,
+      'default',
+      array('target_bundles' => array($this->bundle)),
+      FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED
+    );
+
+  }
+
+  /**
+   * Tests the regular entity serialization.
+   */
+  public function testEntitySerialization() {
+    $entity = $this->container->get('entity_type.manager')
+      ->getStorage($this->entityType)
+      ->create(['type' => $this->bundle, 'name' => 'test entity']);
+
+    $serialized_entity = serialize($entity);
+    $entity = unserialize($serialized_entity);
+
+    $this->assertEquals('test entity', $entity->label());
+  }
+
+  /**
+   * Tests the regular entity serialization with references.
+   */
+  public function testRegularEntitySerializationWithEntityReferences() {
+    $entity = $this->createEntity();
+
+    // Assert that the regular serialization will not serialize references.
+    $original_label = $entity->{$this->fieldName}->entity->label();
+    $entity->{$this->fieldName}->entity->name = 'test referenced entity changed';
+    $serialized_entity = serialize($entity);
+    $entity = unserialize($serialized_entity);
+    $this->assertEquals($original_label, $entity->{$this->fieldName}->entity->label());
+  }
+
+  /**
+   * Tests entity serialization with flag for serializing references.
+   */
+  public function testEntitySerializationWithSerializingEntityReferences() {
+    $entity = $this->createEntity();
+
+    // Assert that using the "serializeFields" flag the serialization will
+    // serialize references.
+    $original_label = $entity->{$this->fieldName}->entity->label();
+    $new_label = 'test referenced entity changed';
+    $this->assertNotEquals($original_label, $new_label);
+
+    $entity->{$this->fieldName}->entity->name = $new_label;
+    $entity->serializeFields = TRUE;
+    $serialized_entity = serialize($entity);
+    $entity = unserialize($serialized_entity);
+    $this->assertEquals($new_label, $entity->{$this->fieldName}->entity->label());
+    // Assert that after unserializing the entity the "serializeFields" flag is
+    // reset.
+    $this->assertTrue(empty($entity->serializeFields));
+    $this->assertTrue(empty($entity->{$this->fieldName}->entity->serializeFields));
+  }
+
+  /**
+   * Tests entity serialization with flag for serializing references - complex.
+   */
+  public function testEntitySerializationWithSerializingEntityReferencesDeeperStructure() {
+    $entity = $this->createEntity();
+
+    // Assert that using the "serializeFields" flag the serialization will
+    // serialize references on a deeper level as well.
+    $original_label_first_reference = $entity->{$this->fieldName}->entity->label();
+    $new_label_first_reference = 'test referenced entity changed';
+    $this->assertNotEquals($original_label_first_reference, $new_label_first_reference);
+    $original_label_second_reference = $entity->{$this->fieldName}->entity->{$this->fieldName}->entity->label();
+    $new_label_second_reference = 'test referenced entity 2 changed';
+    $this->assertNotEquals($original_label_second_reference, $new_label_second_reference);
+
+    $entity->{$this->fieldName}->entity->name = $new_label_first_reference;
+    $entity->{$this->fieldName}->entity->{$this->fieldName}->entity->name = $new_label_second_reference;
+    $entity->serializeFields = TRUE;
+    $serialized_entity = serialize($entity);
+    $entity = unserialize($serialized_entity);
+    $this->assertEquals($new_label_first_reference, $entity->{$this->fieldName}->entity->label());
+    $this->assertEquals($new_label_second_reference, $entity->{$this->fieldName}->entity->{$this->fieldName}->entity->label());
+    // Assert that after unserializing the entity the "serializeFields" flag is
+    // reset.
+    $this->assertTrue(empty($entity->serializeFields));
+    $this->assertTrue(empty($entity->{$this->fieldName}->entity->serializeFields));
+    $this->assertTrue(empty($entity->{$this->fieldName}->entity->{$this->fieldName}->entity->serializeFields));
+  }
+
+  /**
+   * Creates and returns an entity with references.
+   *
+   * @return \Drupal\Core\Entity\EntityTypeInterface
+   *   The entity object.
+   */
+  protected function createEntity() {
+    $referenced_entity = $this->container->get('entity_type.manager')
+      ->getStorage($this->referencedEntityType)
+      ->create(['type' => $this->bundle, 'name' => 'test referenced entity']);
+    $referenced_entity->save();
+
+    $referenced_entity_2 = $this->container->get('entity_type.manager')
+      ->getStorage($this->referencedEntityType)
+      ->create(['type' => $this->bundle, 'name' => 'test referenced entity 2']);
+    $referenced_entity_2->save();
+
+    $entity = $this->container->get('entity_type.manager')
+      ->getStorage($this->entityType)
+      ->create(['type' => $this->bundle, 'name' => 'test entity']);
+
+    $entity->{$this->fieldName}->entity = $referenced_entity;
+    $referenced_entity->{$this->fieldName}->entity = $referenced_entity_2;
+
+    return $entity;
+  }
+
+}