diff --git a/core/modules/system/src/Tests/Theme/ThemeInfoTest.php b/core/modules/system/src/Tests/Theme/ThemeInfoTest.php
index f35ef89208d..b8438bce472 100644
--- a/core/modules/system/src/Tests/Theme/ThemeInfoTest.php
+++ b/core/modules/system/src/Tests/Theme/ThemeInfoTest.php
@@ -99,13 +99,13 @@ class ThemeInfoTest extends WebTestBase {
     $active_theme = $this->themeManager->getActiveTheme();
     // Make sure we are not testing the wrong theme.
     $this->assertEqual('test_theme', $active_theme->getName());
-    $this->assertEqual([], $active_theme->getLibraries());
+    $this->assertEqual(['classy/base'], $active_theme->getLibraries());
 
     // @see theme_test_system_info_alter()
     $this->state->set('theme_test.modify_info_files', TRUE);
     drupal_flush_all_caches();
     $active_theme = $this->themeManager->getActiveTheme();
-    $this->assertEqual(['core/backbone'], $active_theme->getLibraries());
+    $this->assertEqual(['classy/base', 'core/backbone'], $active_theme->getLibraries());
   }
 
 }
diff --git a/core/themes/classy/classy.info.yml b/core/themes/classy/classy.info.yml
index 990896e3ca7..93a52685f0b 100644
--- a/core/themes/classy/classy.info.yml
+++ b/core/themes/classy/classy.info.yml
@@ -5,6 +5,5 @@ package: Core
 version: VERSION
 core: 8.x
 
-stylesheets:
-  all:
-    - css/layout.css
+libraries:
+  - classy/base
diff --git a/core/themes/classy/classy.libraries.yml b/core/themes/classy/classy.libraries.yml
new file mode 100644
index 00000000000..116c86b5e99
--- /dev/null
+++ b/core/themes/classy/classy.libraries.yml
@@ -0,0 +1,5 @@
+base:
+  version: VERSION
+  css:
+    theme:
+      css/layout.css: {}