diff -u b/core/modules/system/src/Tests/Theme/ThemeInfoTest.php b/core/modules/system/src/Tests/Theme/ThemeInfoTest.php
--- b/core/modules/system/src/Tests/Theme/ThemeInfoTest.php
+++ b/core/modules/system/src/Tests/Theme/ThemeInfoTest.php
@@ -56,7 +56,7 @@
   }
 
   /**
-   * Tests stylesheets-override and stylesheets-remove.
+   * Tests stylesheets-remove.
    */
   function testStylesheets() {
     $this->themeHandler->install(array('test_basetheme', 'test_subtheme'));
@@ -65,12 +65,10 @@
       ->save();
 
     $base = drupal_get_path('theme', 'test_basetheme');
-    // Unlike test_basetheme (and the original module CSS), the subtheme decides
-    // to put all of its CSS into a ./css subdirectory. All overrides and
-    // removals are expected to be based on a file's basename and should work
-    // nevertheless.
     $sub = drupal_get_path('theme', 'test_subtheme') . '/css';
 
+    // All removals are expected to be based on a file's path and name and
+    // should work nevertheless.
     $this->drupalGet('theme-test/info/stylesheets');
 
     $this->assertIdentical(1, count($this->xpath("//link[contains(@href, '$base/base-add.css')]")), "$base/base-add.css found");
only in patch2:
unchanged:
--- a/core/modules/system/tests/themes/test_theme/test_theme.info.yml
+++ b/core/modules/system/tests/themes/test_theme/test_theme.info.yml
@@ -15,7 +15,7 @@ version: VERSION
 base theme: classy
 core: 8.x
 stylesheets-remove:
-  - system.module.css
+  - @system/css/system.module.css
 regions:
   content: Content
   left: Left
only in patch2:
unchanged:
--- a/core/themes/stark/stark.info.yml
+++ b/core/themes/stark/stark.info.yml
@@ -7,4 +7,4 @@ core: 8.x
 libraries:
   - stark/global-styling
 stylesheets-remove:
-  - normalize.css
+  - core/assets/vendor/normalize-css/normalize.css