diff --git a/core/lib/Drupal/Component/Plugin/Discovery/DefaultsDecorator.php b/core/lib/Drupal/Component/Plugin/Discovery/DefaultsDecorator.php
index 33aec23..401031a 100644
--- a/core/lib/Drupal/Component/Plugin/Discovery/DefaultsDecorator.php
+++ b/core/lib/Drupal/Component/Plugin/Discovery/DefaultsDecorator.php
@@ -31,13 +31,12 @@ class DefaultsDecorator implements DiscoveryInterface {
   /**
    * Constructs a DefaultsDecorator object.
    *
-   * @param DiscoveryInterface $discovery
+   * @param \Drupal\Component\Plugin\Discovery\DiscoveryInterface $discovery
    *   The parent object implementing DiscoveryInterface that is being
    *   decorated.
    * @param array $defaults
-   *   An array of defaults that will be added to each plugin definition. For
-   *   nested arrays, each array level is merged using
-   *   \Drupal\Component\Utility\NestedArray::mergeDeep().
+   *   An array of defaults that will be merged onto each plugin definition
+   *   using \Drupal\Component\Utility\NestedArray::mergeDeep().
    */
   public function __construct(DiscoveryInterface $decorated, $defaults) {
     $this->decorated = $decorated;
@@ -58,7 +57,7 @@ public function getDefinition($plugin_id) {
   public function getDefinitions() {
     $definitions = $this->decorated->getDefinitions();
     foreach ($definitions as $plugin_id => &$definition) {
-      $definition = NestedArray::mergeDeep($defaults, $definition);
+      $definition = NestedArray::mergeDeep($this->defaults, $definition);
     }
     return $definitions;
   }