diff --git a/core/lib/Drupal/Core/Plugin/Discovery/AnnotatedClassDiscovery.php b/core/lib/Drupal/Core/Plugin/Discovery/AnnotatedClassDiscovery.php
index 015d167..144eda0 100644
--- a/core/lib/Drupal/Core/Plugin/Discovery/AnnotatedClassDiscovery.php
+++ b/core/lib/Drupal/Core/Plugin/Discovery/AnnotatedClassDiscovery.php
@@ -83,7 +83,7 @@ public function getDefinitions() {
     // Get all PSR-0 namespaces.
     $namespaces = drupal_classloader()->getNamespaces();
     // Rewrite all directories.
-    foreach ($namespaces as $ns => &$namespace_dirs) {
+    foreach ($namespaces as $ns => $namespace_dirs) {
       // OS-Safe directory separators.
       $ns = str_replace('\\', DIRECTORY_SEPARATOR, $ns);
       // Check for the pre-determined directory structure to find plugins.
@@ -93,8 +93,8 @@ public function getDefinitions() {
         $this->owner,
         $this->type
       ));
-      foreach ($namespace_dirs as &$dir) {
-        $dir = array(
+      foreach ($namespace_dirs as $key => $dir) {
+        $namespaces[$ns][$key] = array(
           'dir' => $dir .= DIRECTORY_SEPARATOR . $prefix,
           'class_base' => str_replace(
             DIRECTORY_SEPARATOR,