diff --git a/core/modules/block/src/Entity/Block.php b/core/modules/block/src/Entity/Block.php
index a4141b1..f8810a9 100644
--- a/core/modules/block/src/Entity/Block.php
+++ b/core/modules/block/src/Entity/Block.php
@@ -85,13 +85,6 @@ class Block extends ConfigEntityBase implements BlockInterface, EntityWithPlugin
   protected $pluginCollection;
 
   /**
-   * The theme that includes the block plugin for this entity.
-   *
-   * @var string
-   */
-  protected $theme;
-
-  /**
    * {@inheritdoc}
    */
   public function getPlugin() {