diff --git a/core/modules/migrate/src/Plugin/migrate/ConfigurablePluginTrait.php b/core/modules/migrate/src/Plugin/migrate/ConfigurablePluginTrait.php
index 92c9088..ad0b3be 100644
--- a/core/modules/migrate/src/Plugin/migrate/ConfigurablePluginTrait.php
+++ b/core/modules/migrate/src/Plugin/migrate/ConfigurablePluginTrait.php
@@ -5,7 +5,7 @@
 use Drupal\Component\Utility\NestedArray;
 
 /**
- * Provides a re-usable implementation ConfigurablePluginInterface.
+ * Provides a re-usable implementation of ConfigurablePluginInterface.
  *
  * @see \Drupal\migrate\Plugin\migrate\ConfigurablePluginInterface
  */
@@ -32,7 +32,7 @@ public function getConfiguration() {
    * @see \Drupal\Component\Plugin\ConfigurablePluginInterface::setConfiguration()
    */
   public function setConfiguration(array $configuration) {
-    $this->configuration = NestedArray::mergeDeep($this->defaultConfiguration(), $configuration);
+    $this->configuration = NestedArray::mergeDeepArray([$this->defaultConfiguration(), $configuration], TRUE);
   }
 
   /**
@@ -48,29 +48,9 @@ public function defaultConfiguration() {
   }
 
   /**
-   * Calculates dependencies for the configured plugin.
+   * Calculates configuration dependencies for the plugin.
    *
-   * Dependencies are saved in the plugin's configuration entity and are used to
-   * determine configuration synchronization order. For example, if the plugin
-   * integrates with specific user roles, this method should return an array of
-   * dependencies listing the specified roles.
-   *
-   * @return array
-   *   An array of dependencies grouped by type (config, content, module,
-   *   theme). For example:
-   *
-   * @code
-   *   array(
-   *     'config' => array('user.role.anonymous', 'user.role.authenticated'),
-   *     'content' => array('node:article:f0a189e6-55fb-47fb-8005-5bef81c44d6d'),
-   *     'module' => array('node', 'user'),
-   *     'theme' => array('seven'),
-   *   );
-   * @endcode
-   *
-   * @see \Drupal\Core\Config\Entity\ConfigDependencyManager
-   * @see \Drupal\Core\Entity\EntityInterface::getConfigDependencyName()
-   * @see \Drupal\Component\Plugin\DependentPluginInterface::calculateDependencies()
+   * Migration plugins are not configuration, so they have no dependencies.
    */
   public final function calculateDependencies() {
     return [];