diff --git a/core/lib/Drupal/Core/Asset/LibraryDiscovery.php b/core/lib/Drupal/Core/Asset/LibraryDiscovery.php
index 5b5c811..46ad1ed 100644
--- a/core/lib/Drupal/Core/Asset/LibraryDiscovery.php
+++ b/core/lib/Drupal/Core/Asset/LibraryDiscovery.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Asset;
 
+use Drupal\Core\Cache\Cache;
 use Drupal\Core\Cache\CacheBackendInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 
@@ -112,7 +113,7 @@ protected function loadLibraryDefinitions() {
     }
     else {
       $libraries = $this->discoveryParser->build();
-      $this->cache->set($this->cacheKey, $libraries);
+      $this->cache->set($this->cacheKey, $libraries, Cache::PERMANENT, ['extension']);
     }
 
     // @todo Should themes be able to take part in this process as well?
diff --git a/core/modules/system/src/Form/ThemeAdminForm.php b/core/modules/system/src/Form/ThemeAdminForm.php
index 2cee8c5..9cf656c 100644
--- a/core/modules/system/src/Form/ThemeAdminForm.php
+++ b/core/modules/system/src/Form/ThemeAdminForm.php
@@ -52,6 +52,7 @@ public function buildForm(array $form, FormStateInterface $form_state, array $th
   public function submitForm(array &$form, FormStateInterface $form_state) {
     drupal_set_message($this->t('The configuration options have been saved.'));
     $this->config('system.theme')->set('admin', $form_state->getValue('admin_theme'))->save();
+    \Drupal::cache('discovery')->delete('library_info');
   }
 
 }
diff --git a/core/modules/system/src/Tests/Common/JavaScriptTest.php b/core/modules/system/src/Tests/Common/JavaScriptTest.php
index a59d50e..a2c6089 100644
--- a/core/modules/system/src/Tests/Common/JavaScriptTest.php
+++ b/core/modules/system/src/Tests/Common/JavaScriptTest.php
@@ -612,7 +612,7 @@ function testGetLibrary() {
     $library_discovery = \Drupal::service('library.discovery');
     // Retrieve all libraries registered by a module.
     $libraries = $library_discovery->getLibrariesByExtension('common_test');
-    $this->assertTrue(isset($libraries['jquery.farbtastic']), 'Retrieved all module libraries.');
+    $this->assertTrue(isset($libraries['common_test/jquery.farbtastic']), 'Retrieved all module libraries.');
     // Retrieve all libraries for a module not declaring any libraries.
     // Note: This test installs language module.
     $libraries = $library_discovery->getLibrariesByExtension('dblog');
diff --git a/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php b/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
index 0c3fbff..5cd2776 100644
--- a/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
+++ b/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
@@ -143,8 +143,14 @@ public function testBuildByExtensionWithMissingLibraryFile() {
         'example_module' => new Extension($this->root, 'module', $path . '/example_module.info.yml')
       ]);
 
-
-    $this->assertSame($this->libraryDiscoveryParser->build(), []);
+    $result = $this->libraryDiscoveryParser->build();
+    foreach ($result as $library_name => $library) {
+      if (strpos($library_name, 'core/') === 0) {
+        unset($result[$library_name]);
+      }
+    }
+
+    $this->assertSame($result, []);
   }
 
   /**