diff --git a/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
index e212720..729ff78 100644
--- a/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -371,8 +371,8 @@ protected function buildContainer() {
 
     // Get a list of namespaces and put it onto the container.
     $namespaces = $this->getModuleNamespaces($this->getModuleFileNames());
-    $namespaces['Drupal\Core'] = DRUPAL_ROOT . '/core/lib/Drupal/Core';
-    $namespaces['Drupal\Component'] = DRUPAL_ROOT . '/core/lib/Drupal/Component';
+    $namespaces['Drupal\Core'] = DRUPAL_ROOT . '/core/lib';
+    $namespaces['Drupal\Component'] = DRUPAL_ROOT . '/core/lib';
     $container->setParameter('container.namespaces', $namespaces);
 
     // Register synthetic services.
diff --git a/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorPluginManagerTest.php b/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorPluginManagerTest.php
index fc56910..b7383d7 100644
--- a/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorPluginManagerTest.php
+++ b/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorPluginManagerTest.php
@@ -63,7 +63,7 @@ function setUp() {
    * Tests the enabling of plugins.
    */
   function testEnabledPlugins() {
-    $this->manager = new CKEditorPluginManager();
+    $this->manager = new CKEditorPluginManager($this->container->getParameter('container.namespaces'));
     $editor = entity_load('editor', 'filtered_html');
 
     // Case 1: no CKEditor plugins.
@@ -77,6 +77,7 @@ function testEnabledPlugins() {
     // variations of it, to cover all possible ways a plugin can be enabled) and
     // clear the editor manager's cache so it is picked up.
     $this->enableModules(array('ckeditor_test'));
+    $this->manager = new CKEditorPluginManager($this->container->getParameter('container.namespaces'));
     $this->manager->clearCachedDefinitions();
 
     // Case 2: CKEditor plugins are available.
diff --git a/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorTest.php b/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorTest.php
index a71a725..fbfb93b 100644
--- a/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorTest.php
+++ b/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorTest.php
@@ -64,7 +64,7 @@ function setUp() {
     $editor->save();
 
     // Create "CKEditor" text editor plugin instance.
-    $manager = new EditorManager();
+    $manager = new EditorManager($this->container->getParameter('container.namespaces'));
     $this->ckeditor = $manager->createInstance('ckeditor');
   }
 
diff --git a/core/modules/system/lib/Drupal/system/Tests/Plugin/Discovery/AnnotatedClassDiscoveryTest.php b/core/modules/system/lib/Drupal/system/Tests/Plugin/Discovery/AnnotatedClassDiscoveryTest.php
index 34670fc..eb08a1a 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Plugin/Discovery/AnnotatedClassDiscoveryTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Plugin/Discovery/AnnotatedClassDiscoveryTest.php
@@ -53,7 +53,7 @@ public function setUp() {
         'class' => 'Drupal\plugin_test\Plugin\plugin_test\fruit\Orange',
       ),
     );
-    $namespaces = array('Drupal\plugin_test' => array(DRUPAL_ROOT . '/core/modules/system/tests/modules/plugin_test/lib'));
+    $namespaces = array('Drupal\plugin_test' => DRUPAL_ROOT . '/core/modules/system/tests/modules/plugin_test/lib');
     $this->discovery = new AnnotatedClassDiscovery('plugin_test', 'fruit', $namespaces);
     $this->emptyDiscovery = new AnnotatedClassDiscovery('non_existing_module', 'non_existing_plugin_type', $namespaces);
   }