diff --git a/core/modules/block/lib/Drupal/block/Annotation/Block.php b/core/modules/block/lib/Drupal/block/Annotation/Block.php
index 64987e6bef57bd4747818b48ebc81b55f17861ab..ec093be5cb0ebd8c658cec9f3613ee3777a96406 100644
--- a/core/modules/block/lib/Drupal/block/Annotation/Block.php
+++ b/core/modules/block/lib/Drupal/block/Annotation/Block.php
@@ -32,4 +32,20 @@ class Block extends Plugin {
    */
   public $admin_label = '';
 
+  /**
+   * The category in the admin UI where the block will be listed.
+   *
+   * @var \Drupal\Core\Annotation\Translation
+   *
+   * @ingroup plugin_translatable
+   */
+  public $category = '';
+
+  /**
+   * Class used to retrieve derivative definitions of the block.
+   *
+   * @var string
+   */
+  public $derivative = '';
+
 }
diff --git a/core/modules/block/lib/Drupal/block/Plugin/Type/BlockManager.php b/core/modules/block/lib/Drupal/block/Plugin/Type/BlockManager.php
index bb76ec25cfaf5fcdee41c422143eb8b3c079c269..e6252ebdd2ad5916a62ba3f42e7b6061c7ee0fb8 100644
--- a/core/modules/block/lib/Drupal/block/Plugin/Type/BlockManager.php
+++ b/core/modules/block/lib/Drupal/block/Plugin/Type/BlockManager.php
@@ -61,7 +61,7 @@ public function processDefinition(&$definition, $plugin_id) {
     parent::processDefinition($definition, $plugin_id);
 
     // Ensure that every block has a category.
-    if (!isset($definition['category'])) {
+    if (empty($definition['category'])) {
       $definition['category'] = $this->getModuleName($definition['provider']);
     }
   }