diff --git a/core/lib/Drupal/Core/Asset/Exception/InvalidCssCategoryException.php b/core/lib/Drupal/Core/Asset/Exception/InvalidCssCategoryException.php
deleted file mode 100644
index b128324..0000000
--- a/core/lib/Drupal/Core/Asset/Exception/InvalidCssCategoryException.php
+++ /dev/null
@@ -1,15 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\Core\Asset\Exception\InvalidCssCategoryException.
- */
-
-namespace Drupal\Core\Asset\Exception;
-
-/**
- * Defines an exception if the library file does not specify a valid category.
- */
-class InvalidCssCategoryException extends \RunTimeException {
-
-}
diff --git a/core/lib/Drupal/Core/Asset/Exception/InvalidDefinitionOfCssException.php b/core/lib/Drupal/Core/Asset/Exception/InvalidCssDefinitionException.php
similarity index 51%
rename from core/lib/Drupal/Core/Asset/Exception/InvalidDefinitionOfCssException.php
rename to core/lib/Drupal/Core/Asset/Exception/InvalidCssDefinitionException.php
index 52d5b5a..def8439 100644
--- a/core/lib/Drupal/Core/Asset/Exception/InvalidDefinitionOfCssException.php
+++ b/core/lib/Drupal/Core/Asset/Exception/InvalidCssDefinitionException.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\Core\Asset\Exception\InvalidDefinitionOfCssException.
+ * Contains \Drupal\Core\Asset\Exception\InvalidCssDefinitionException.
  */
 
 namespace Drupal\Core\Asset\Exception;
@@ -10,6 +10,6 @@
 /**
  * Defines an exception if the library file is not keyed by a category.
  */
-class InvalidDefinitionOfCssException extends \RunTimeException {
+class InvalidCssDefinitionException extends \RunTimeException {
 
 }
diff --git a/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php b/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
index 09c4e84..b3354dc 100644
--- a/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
+++ b/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
@@ -8,8 +8,7 @@
 namespace Drupal\Core\Asset;
 
 use Drupal\Core\Asset\Exception\IncompleteLibraryDefinitionException;
-use Drupal\Core\Asset\Exception\InvalidCssCategoryException;
-use Drupal\Core\Asset\Exception\InvalidDefinitionOfCssException;
+use Drupal\Core\Asset\Exception\InvalidCssDefinitionException;
 use Drupal\Core\Asset\Exception\InvalidLibraryFileException;
 use Drupal\Core\Asset\Exception\LibraryDefinitionMissingLicenseException;
 use Drupal\Core\Extension\ModuleHandlerInterface;
@@ -125,19 +124,19 @@ public function buildByExtension($extension) {
         if ($type == 'css' && !empty($library[$type])) {
           foreach ($library[$type] as $category => $files) {
             if (empty($files)) {
-              throw new InvalidDefinitionOfCssException(sprintf("You have to key the css files in the %s.library.yml file by category ('%s' seems to be a file name, allowed categories are Base, Layout, Component, State, Theme)", $extension, $category));
+              throw new InvalidCssDefinitionException(sprintf("You have to key the css files in the %s.library.yml file by category ('%s' seems to be a file name, allowed categories are Base, Layout, Component, State, Theme)", $extension, $category));
             }
             foreach ($files as $source => $options) {
               if (!isset($options['weight'])) {
                 $options['weight'] = 0;
               }
-              //Check if the category is valid or not and
-              //  apply the corresponding weight defined by CSS_* constants.
+              // Check if the category is valid or not and apply the
+              // corresponding weight defined by the CSS_* constants.
               if (defined('CSS_' . strtoupper($category))) {
                 $options['weight'] += constant('CSS_' . strtoupper($category));
               }
               else {
-                throw new InvalidCssCategoryException(sprintf("You have used an invalid category %s in %s.libraries.yml. Allowed categories are Base, Layout, Component, State, Theme)", $category, $extension));
+                throw new InvalidCssDefinitionException(sprintf("You have used an invalid category %s in %s.libraries.yml. Allowed categories are Base, Layout, Component, State, Theme)", $category, $extension));
               }
               $library[$type][$source] = $options;
             }
diff --git a/core/modules/system/tests/modules/common_test/common_test.module b/core/modules/system/tests/modules/common_test/common_test.module
index 1195374..f89e772 100644
--- a/core/modules/system/tests/modules/common_test/common_test.module
+++ b/core/modules/system/tests/modules/common_test/common_test.module
@@ -174,9 +174,11 @@ function common_test_library_info_build() {
   if (\Drupal::state()->get('common_test.library_info_build_test')) {
     $libraries['dynamic_library'] = [
       'version' => '1.0',
-      'css' => ['theme' => [
-        'common_test.css' => [],
-      ]],
+      'css' => [
+        'theme' => [
+          'common_test.css' => [],
+        ],
+      ],
     ];
   }
   return $libraries;