diff --git a/core/modules/block/custom_block/src/Plugin/Derivative/CustomBlock.php b/core/modules/block/custom_block/src/Plugin/Derivative/CustomBlock.php
deleted file mode 100644
index 976703d..0000000
--- a/core/modules/block/custom_block/src/Plugin/Derivative/CustomBlock.php
+++ /dev/null
@@ -1,28 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\custom_block\Plugin\Derivative\CustomBlock.
- */
-
-namespace Drupal\custom_block\Plugin\Derivative;
-
-use Drupal\Component\Plugin\Derivative\DeriverBase;
-use Drupal\Core\Plugin\Discovery\ContainerDeriverInterface;
-
-/**
- * Retrieves block plugin definitions for all custom blocks.
- */
-class CustomBlock extends DeriverBase {
-  /**
-   * {@inheritdoc}
-   */
-  public function getDerivativeDefinitions($base_plugin_definition) {
-    $custom_blocks = entity_load_multiple('custom_block');
-    foreach ($custom_blocks as $custom_block) {
-      $this->derivatives[$custom_block->uuid()] = $base_plugin_definition;
-      $this->derivatives[$custom_block->uuid()]['admin_label'] = $custom_block->label();
-    }
-    return parent::getDerivativeDefinitions($base_plugin_definition);
-  }
-}
diff --git a/core/modules/block_content/src/Tests/BlockContentSaveTest.php b/core/modules/block_content/src/Tests/BlockContentSaveTest.php
index 9c1b984..1c8a962 100644
--- a/core/modules/block_content/src/Tests/BlockContentSaveTest.php
+++ b/core/modules/block_content/src/Tests/BlockContentSaveTest.php
@@ -8,7 +8,6 @@
 namespace Drupal\block_content\Tests;
 
 use Drupal\block_content\Entity\BlockContent;
-use Drupal\custom_block\Entity\CustomBlock;
 
 /**
  * Tests block save related functionality.
diff --git a/core/modules/migrate_drupal/src/Tests/d6/MigrateBlockContentTest.php b/core/modules/migrate_drupal/src/Tests/d6/MigrateBlockContentTest.php
index b6c2321..460371a 100644
--- a/core/modules/migrate_drupal/src/Tests/d6/MigrateBlockContentTest.php
+++ b/core/modules/migrate_drupal/src/Tests/d6/MigrateBlockContentTest.php
@@ -10,7 +10,6 @@
 use Drupal\Core\Language\Language;
 use Drupal\block_content\Entity\BlockContent;
 use Drupal\Core\Language\LanguageInterface;
-use Drupal\custom_block\Entity\CustomBlock;
 use Drupal\migrate\MigrateExecutable;
 use Drupal\migrate_drupal\Tests\MigrateDrupalTestBase;