diff --git a/core/modules/block/lib/Drupal/block/BlockPluginBag.php b/core/modules/block/lib/Drupal/block/BlockPluginBag.php
new file mode 100644
index 0000000..4247398
--- /dev/null
+++ b/core/modules/block/lib/Drupal/block/BlockPluginBag.php
@@ -0,0 +1,74 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\block\BlockPluginBag.
+ */
+
+namespace Drupal\block;
+
+use Drupal\Component\Plugin\PluginBag;
+use Drupal\Component\Plugin\PluginManagerInterface;
+use Drupal\Component\Plugin\Exception\PluginException;
+use Drupal\block\Plugin\Core\Entity\Block;
+
+/**
+ * Defines a plugin bag for storing block plugins.
+ *
+ * @see \Drupal\block\Plugin\Type\BlockManager
+ */
+class BlockPluginBag extends PluginBag {
+
+  /**
+   * Stores the plugin manager used by this bag.
+   *
+   * @var \Drupal\Component\Plugin\PluginManagerInterface
+   */
+  protected $manager;
+
+  /**
+   * Stores a reference to the block that uses this bag.
+   *
+   * @var \Drupal\block\Plugin\Core\Entity\Block
+   */
+  protected $block;
+
+  /**
+   * Constructs a BlockPluginBag object.
+   *
+   * @param \Drupal\block\Plugin\Core\Entity\Block $block
+   *   The Block that contains this plugin bag.
+   * @param \Drupal\Component\Plugin\PluginManagerInterface $manager
+   *   The plugin manager that handles block plugins.
+   */
+  public function __construct(Block $block, PluginManagerInterface $manager) {
+    $this->instanceIDs = array($block->get('plugin'));
+    $this->manager = $manager;
+    $this->block = $block;
+  }
+
+  /**
+   * Implements \Drupal\Component\Plugin\PluginBag::initializePlugin().
+   */
+  protected function initializePlugin($instance_id) {
+    // If the plugin was initialized before, just return.
+    if (isset($this->pluginInstances[$instance_id])) {
+      return;
+    }
+
+    try {
+      $configuration = $this->block->get('configuration');
+      $this->pluginInstances[$instance_id] = $this->manager->createInstance($instance_id, $configuration);
+      $configuration += $this->pluginInstances[$instance_id]->getConfig();
+      $this->block->set('configuration', $configuration);
+    }
+    catch (PluginException $e) {
+      // Ignore blocks belonging to disabled modules, but re-throw valid
+      // exceptions when the module is enabled and the plugin is misconfigured.
+      if (module_exists($this->block->get('module'))) {
+        throw $e;
+      }
+    }
+  }
+
+}
diff --git a/core/modules/block/lib/Drupal/block/Plugin/Core/Entity/Block.php b/core/modules/block/lib/Drupal/block/Plugin/Core/Entity/Block.php
index e8ccc63..fbe36b1 100644
--- a/core/modules/block/lib/Drupal/block/Plugin/Core/Entity/Block.php
+++ b/core/modules/block/lib/Drupal/block/Plugin/Core/Entity/Block.php
@@ -10,7 +10,7 @@
 use Drupal\Core\Config\Entity\ConfigEntityBase;
 use Drupal\Core\Annotation\Plugin;
 use Drupal\Core\Annotation\Translation;
-use Drupal\Component\Plugin\Exception\PluginException;
+use Drupal\block\BlockPluginBag;
 
 /**
  * Defines a Block configuration entity class.
@@ -128,26 +128,29 @@ class Block extends ConfigEntityBase {
   protected $plugin;
 
   /**
+   * Stores instantiated plugins for this block.
+   *
+   * @var \Drupal\block\BlockPluginBag
+   */
+  protected $pluginBag;
+
+  /**
+   * Overrides \Drupal\Core\Config\Entity\ConfigEntityBase::__construct();
+   */
+  public function __construct(array $values, $entity_type) {
+    parent::__construct($values, $entity_type);
+
+    $this->pluginBag = new BlockPluginBag($this, drupal_container()->get('plugin.manager.block'));
+  }
+
+  /**
    * Returns the plugin instance.
    *
    * @return \Drupal\block\BlockInterface
    *   The plugin instance for this block.
    */
   public function getPlugin() {
-    if (!$this->instance) {
-      try {
-        $this->instance = drupal_container()->get('plugin.manager.block')->createInstance($this->plugin, $this->configuration);
-        $this->configuration += $this->instance->getConfig();
-      }
-      catch (PluginException $e) {
-        // Ignore blocks belonging to disabled modules, but re-throw valid
-        // exceptions when the module is enabled and the plugin is misconfigured.
-        if (module_exists($this->module)) {
-          throw $e;
-        }
-      }
-    }
-    return $this->instance;
+    return $this->pluginBag->get($this->plugin);
   }
 
   /**