diff --git a/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php b/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
index 56603c7..547e415 100644
--- a/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
@@ -24,7 +24,7 @@
  *
  * @ingroup entity_api
  */
-abstract class ConfigEntityBase extends Entity implements ConfigEntityInterface {
+abstract class ConfigEntityBase extends Entity implements ConfigEntityInterface, \Serializable {
 
   use PluginDependencyTrait {
     addDependency as addDependencyTrait;
@@ -612,4 +612,43 @@ public function save() {
     return $return;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function serialize() {
+    if ($this->getEntityType()->get('config_export')) {
+      $data = [
+        'entity_type_id' => $this->getEntityTypeId(),
+        'is_new' => $this->isNew(),
+        'values' => $this->toArray(),
+      ];
+      return serialize(['__smart_serialize' => $data]);
+    }
+    else {
+      return serialize(get_object_vars($this));
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function unserialize($serialized) {
+    $unserialized = unserialize($serialized);
+    // PHPUnit uses unserialize() on a made up string as a trick when bypassing
+    // the contructor on mock object creation. Make sure we only run on objects
+    // that have been serialized through our serialize() method.
+    if (is_array($unserialized)) {
+      if (isset($unserialized['__smart_serialize'])) {
+        $data = $unserialized['__smart_serialize'];
+        $this->__construct($data['values'], $data['entity_type_id']);
+        $this->enforceIsNew($data['is_new']);
+      }
+      else {
+        foreach ($unserialized as $name => $value) {
+          $this->$name = $value;
+        }
+      }
+    }
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Field/FieldConfigBase.php b/core/lib/Drupal/Core/Field/FieldConfigBase.php
index fa34ca3..8731359 100644
--- a/core/lib/Drupal/Core/Field/FieldConfigBase.php
+++ b/core/lib/Drupal/Core/Field/FieldConfigBase.php
@@ -419,21 +419,6 @@ public function getDefaultValue(FieldableEntityInterface $entity) {
   }
 
   /**
-   * Implements the magic __sleep() method.
-   *
-   * Using the Serialize interface and serialize() / unserialize() methods
-   * breaks entity forms in PHP 5.4.
-   * @todo Investigate in https://drupal.org/node/2074253.
-   */
-  public function __sleep() {
-    // Only serialize necessary properties, excluding those that can be
-    // recalculated.
-    $properties = get_object_vars($this);
-    unset($properties['fieldStorage'], $properties['itemDefinition'], $properties['bundleRenameAllowed'], $properties['original']);
-    return array_keys($properties);
-  }
-
-  /**
    * {@inheritdoc}
    */
   public static function createFromItemType($item_type) {
diff --git a/core/modules/field/src/Entity/FieldStorageConfig.php b/core/modules/field/src/Entity/FieldStorageConfig.php
index 97db63f..ace5384 100644
--- a/core/modules/field/src/Entity/FieldStorageConfig.php
+++ b/core/modules/field/src/Entity/FieldStorageConfig.php
@@ -697,21 +697,6 @@ public function hasData() {
   }
 
   /**
-   * Implements the magic __sleep() method.
-   *
-   * Using the Serialize interface and serialize() / unserialize() methods
-   * breaks entity forms in PHP 5.4.
-   * @todo Investigate in https://drupal.org/node/2074253.
-   */
-  public function __sleep() {
-    // Only serialize necessary properties, excluding those that can be
-    // recalculated.
-    $properties = get_object_vars($this);
-    unset($properties['schema'], $properties['propertyDefinitions'], $properties['original']);
-    return array_keys($properties);
-  }
-
-  /**
    * {@inheritdoc}
    */
   public function getConstraints() {
diff --git a/core/modules/tour/tests/src/Unit/Entity/TourTest.php b/core/modules/tour/tests/src/Unit/Entity/TourTest.php
index a6625c8..93526e9 100644
--- a/core/modules/tour/tests/src/Unit/Entity/TourTest.php
+++ b/core/modules/tour/tests/src/Unit/Entity/TourTest.php
@@ -6,6 +6,7 @@
 
 namespace Drupal\Tests\tour\Unit\Entity;
 
+use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\Tests\UnitTestCase;
 
 /**
@@ -31,8 +32,17 @@ class TourTest extends UnitTestCase {
    * @dataProvider routeProvider
    */
   public function testHasMatchingRoute($routes, $route_name, $route_params, $result) {
-    $tour = $this->getMockBuilder('\Drupal\tour\Entity\Tour')
+    // Tour::__construct() pulls the plugin.manager.tour.tip service from the
+    // container. Mock it and and place it there.
+    $tip_manager = $this->getMockBuilder('Drupal\tour\TipPluginManager')
       ->disableOriginalConstructor()
+      ->getMock();
+    $container = new ContainerBuilder();
+    $container->set('plugin.manager.tour.tip', $tip_manager);
+    \Drupal::setContainer($container);
+
+    $tour = $this->getMockBuilder('\Drupal\tour\Entity\Tour')
+      ->setConstructorArgs(array(array(), 'tour'))
       ->setMethods(array('getRoutes'))
       ->getMock();