diff --git a/composer.lock b/composer.lock
index 4440df740b1..c4ef18e6d12 100644
--- a/composer.lock
+++ b/composer.lock
@@ -530,7 +530,7 @@
             "dist": {
                 "type": "path",
                 "url": "core",
-                "reference": "84de0d6ef4eda33dd426005557f64496a2fd02d1"
+                "reference": "874a51210b265aa07599dc966748e43cf31a0321"
             },
             "require": {
                 "asm89/stack-cors": "^1.1",
@@ -759,6 +759,7 @@
                     "lib/Drupal/Core/Site/Settings.php"
                 ],
                 "files": [
+                    "class_aliases.php",
                     "includes/bootstrap.inc"
                 ]
             },
diff --git a/core/class_aliases.php b/core/class_aliases.php
new file mode 100644
index 00000000000..f058962f842
--- /dev/null
+++ b/core/class_aliases.php
@@ -0,0 +1,12 @@
+<?php
+
+/**
+ * @file
+ * Contains class_aliases that will be added by the autoloader.
+ *
+ * @see core/composer.json
+ */
+
+// @todo https://www.drupal.org/project/drupal/issues/3197482 Remove this class
+//   alias once Drupal is running Symfony 5.3 or higher.
+class_alias('Drupal\Core\Http\KernelEvent', 'Symfony\Component\HttpKernel\Event\KernelEvent', TRUE);
diff --git a/core/composer.json b/core/composer.json
index aeb57cbf8f9..b71a1889075 100644
--- a/core/composer.json
+++ b/core/composer.json
@@ -201,7 +201,10 @@
             "lib/Drupal/Core/Installer/InstallerRedirectTrait.php",
             "lib/Drupal/Core/Site/Settings.php"
         ],
-        "files": [ "includes/bootstrap.inc" ]
+        "files": [
+            "class_aliases.php",
+            "includes/bootstrap.inc"
+        ]
     },
     "config": {
         "preferred-install": "dist"
diff --git a/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
index d9af456bbde..599e13833ad 100644
--- a/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -18,7 +18,6 @@ use Drupal\Core\DependencyInjection\YamlFileLoader;
 use Drupal\Core\Extension\ExtensionDiscovery;
 use Drupal\Core\File\MimeType\MimeTypeGuesser;
 use Drupal\Core\Http\InputBag;
-use Drupal\Core\Http\KernelEvent;
 use Drupal\Core\Http\TrustedHostsRequestFactory;
 use Drupal\Core\Installer\InstallerKernel;
 use Drupal\Core\Installer\InstallerRedirectTrait;
@@ -40,10 +39,6 @@ use TYPO3\PharStreamWrapper\Manager as PharStreamWrapperManager;
 use TYPO3\PharStreamWrapper\Behavior as PharStreamWrapperBehavior;
 use TYPO3\PharStreamWrapper\PharStreamWrapper;
 
-// @todo https://www.drupal.org/project/drupal/issues/3197482 Remove this class
-//   alias once Drupal is running Symfony 5.3 or higher.
-class_alias(KernelEvent::class, 'Symfony\Component\HttpKernel\Event\KernelEvent', TRUE);
-
 /**
  * The DrupalKernel class is the core of Drupal itself.
  *
diff --git a/core/tests/Drupal/Tests/Core/DrupalKernel/DrupalKernelLegacyTest.php b/core/tests/Drupal/Tests/Core/DrupalKernel/DrupalKernelLegacyTest.php
index f07abf258f6..adca11d8054 100644
--- a/core/tests/Drupal/Tests/Core/DrupalKernel/DrupalKernelLegacyTest.php
+++ b/core/tests/Drupal/Tests/Core/DrupalKernel/DrupalKernelLegacyTest.php
@@ -19,7 +19,7 @@ class DrupalKernelLegacyTest extends UnitTestCase {
    * @covers ::isMasterRequest
    */
   public function testKernelEventDeprecation() {
-    $kernel = new DrupalKernel('test', NULL);
+    $kernel = $this->createMock(DrupalKernel::class);
     $request = $this->createMock(Request::class);
     $event = new KernelEvent($kernel, $request, $kernel::MASTER_REQUEST);