diff --git a/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php b/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
index a95c2ff..fa74923 100644
--- a/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
+++ b/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
@@ -52,7 +52,7 @@ class LibraryDiscoveryParser {
    * libraries-override behavior where overriding of already overridden paths
    * required using the full Drupal-root-relative path of the last override.
    *
-   * @todo Remove when BC-break is allowed.
+   * @todo Remove BC layer in Drupal 9.0.0 https://www.drupal.org/node/2852314.
    *
    * @var array
    */
@@ -163,9 +163,12 @@ public function buildByExtension($extension) {
         }
         foreach ($library[$type] as $source => $options) {
           unset($library[$type][$source]);
-          // Update to the overridden source in libraries-override.
-          if (!($source = $this->getLatestOverridePath($source, $type, $id, $extension))) {
-            // Don't bother if the override says 'false'.
+          // Get the actual overridden path to $source in libraries-override.
+          $source = $this->getLatestOverridePath($source, $type, $id, $extension);
+          if (!$source) {
+            // If $source is false, it means that a libraries-override entry in
+            // the theme or base theme has specified that the library should be
+            // removed. Hence this entry should not be processed.
             continue;
           }
           // Allow to omit the options hashmap in YAML declarations.
@@ -446,11 +449,11 @@ protected function isValidUri($string) {
    */
   protected function setOverrideValue(array $overrides, $type, $library_name, $extension, $theme_path) {
     foreach ($overrides as $original => $replacement) {
-      // $original can either be the last overridden path (also possibly
-      // using the '@themename' token) or the original library definition path.
+      // $original can either be the last overridden path or the original
+      // library definition path.
 
       // For BC we check if $original still refers to base-theme overrides.
-      // @todo Remove when BC-break is allowed.
+      // @todo Remove BC in Drupal 9.0.0 https://www.drupal.org/node/2852314.
       if (isset($this->originalLibraryPaths[$original])) {
         // Here $original actually refers to an overridden path (maybe from a
         // base theme), so get the actual original path by which the library
@@ -471,10 +474,11 @@ protected function setOverrideValue(array $overrides, $type, $library_name, $ext
    * @param string $theme_path
    *   The theme or base theme.
    * @param string|false $overriding_asset
-   *   The overriding library asset.
+   *   The overriding library asset or false for asset removal.
    *
-   * @return string
-   *   A fully resolved theme asset path relative to the Drupal directory.
+   * @return string|false
+   *   A fully resolved theme asset path relative to the Drupal directory or
+   *   false if the asset is to be removed.
    */
   protected function resolveThemeAssetPath($theme_path, $overriding_asset) {
     if ($overriding_asset == FALSE) {
@@ -501,9 +505,10 @@ protected function resolveThemeAssetPath($theme_path, $overriding_asset) {
    * @param string $extension
    *   The extension name.
    *
-   * @return string
+   * @return string|false
    *   The full path to the effective libraries-override asset or $original_path
-   *   if the asset is not overridden.
+   *   if the asset is not overridden. Returns false if the asset is to be
+   *   removed.
    */
   protected function getLatestOverridePath($original_path, $type, $library_name, $extension) {
     $key = $extension . ':' . $library_name . ':' . $type . ':' . $original_path;
@@ -515,8 +520,9 @@ protected function getLatestOverridePath($original_path, $type, $library_name, $
   /**
    * Sets the libraries-override path that applies to the library asset.
    *
-   * @param string $new_path
-   *   The Drupal-root-relative path to the overriding library asset.
+   * @param string|false $new_path
+   *   The Drupal-root-relative path to the overriding library asset or false if
+   *   the asset is to be removed.
    * @param string $original_path
    *   The original library asset source path.
    * @param string $type
diff --git a/core/modules/system/tests/themes/test_basetheme/test_basetheme.info.yml b/core/modules/system/tests/themes/test_basetheme/test_basetheme.info.yml
index 3efb45f..6c621ff 100644
--- a/core/modules/system/tests/themes/test_basetheme/test_basetheme.info.yml
+++ b/core/modules/system/tests/themes/test_basetheme/test_basetheme.info.yml
@@ -18,6 +18,10 @@ libraries-override:
     css:
       component:
         assets/vendor/farbtastic/farbtastic.css: css/farbtastic.css
+  core/normalize:
+    css:
+        base:
+          assets/vendor/normalize-css/normalize.css: css/normalize.css
 
 libraries-extend:
   classy/base:
diff --git a/core/modules/system/tests/themes/test_subsubtheme/test_subsubtheme.info.yml b/core/modules/system/tests/themes/test_subsubtheme/test_subsubtheme.info.yml
index e254a48..c5f3a25 100644
--- a/core/modules/system/tests/themes/test_subsubtheme/test_subsubtheme.info.yml
+++ b/core/modules/system/tests/themes/test_subsubtheme/test_subsubtheme.info.yml
@@ -14,3 +14,7 @@ libraries-override:
       component:
         # Tests previous behavior of using the last overridden path.
         /core/modules/system/tests/themes/test_basetheme/css/farbtastic.css: css/subsubtheme-farbtastic.css
+  core/normalize:
+    css:
+        base:
+          assets/vendor/normalize-css/normalize.css: false
diff --git a/core/tests/Drupal/KernelTests/Core/Asset/LibraryDiscoveryIntegrationTest.php b/core/tests/Drupal/KernelTests/Core/Asset/LibraryDiscoveryIntegrationTest.php
index addf6d8..5288d6f 100644
--- a/core/tests/Drupal/KernelTests/Core/Asset/LibraryDiscoveryIntegrationTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Asset/LibraryDiscoveryIntegrationTest.php
@@ -164,11 +164,20 @@ public function testBaseThemeLibrariesOverrideInSubTheme() {
    * Tests library-override on already overridden libraries.
    */
   public function testLibrariesOverrideOverridden() {
+    // Activate a sub-theme that doesn't override a library override.
+    $this->activateTheme('test_subtheme');
+
+    // Assert that effective libraries override is from the test_subsubtheme.
+    $this->assertAssetInLibrary('core/modules/system/tests/themes/test_basetheme/css/farbtastic.css', 'core', 'jquery.farbtastic', 'css');
+    $this->assertAssetInLibrary('core/modules/system/tests/themes/test_basetheme/css/normalize.css', 'core', 'normalize', 'css');
+
     // Activate a sub-theme that overrides a library override.
     $this->activateTheme('test_subsubtheme');
 
     // Assert that effective libraries override is from the test_subsubtheme.
     $this->assertNoAssetInLibrary('core/modules/system/tests/themes/test_basetheme/css/farbtastic.css', 'core', 'jquery.farbtastic', 'css');
+    $this->assertNoAssetInLibrary('core/modules/system/tests/themes/test_basetheme/css/normalize.css', 'core', 'normalize', 'css');
+    $this->assertNoAssetInLibrary('core/assets/vendor/normalize-css/normalize.css', 'core', 'normalize', 'css');
     $this->assertAssetInLibrary('core/modules/system/tests/themes/test_subsubtheme/css/subsubtheme-farbtastic.css', 'core', 'jquery.farbtastic', 'css');
     $this->assertAssetInLibrary('core/modules/system/tests/themes/test_subsubtheme/js/subsubtheme-dialog.js', 'core', 'drupal.dialog', 'js');
   }