diff --git a/composer.json b/composer.json
index 63b08d9a2d..ee812601cb 100644
--- a/composer.json
+++ b/composer.json
@@ -86,14 +86,18 @@
     "autoload-dev": {
         "psr-4": {
             "Drupal\\Composer\\": "composer"
-        }
+        },
+        "files": [ "core/includes/class_aliases_dev.php" ]
     },
     "scripts": {
         "pre-install-cmd": "Drupal\\Composer\\Composer::ensureComposerVersion",
         "pre-update-cmd": "Drupal\\Composer\\Composer::ensureComposerVersion",
         "pre-autoload-dump": "Drupal\\Core\\Composer\\Composer::preAutoloadDump",
         "drupal-phpunit-upgrade-check": "Drupal\\Core\\Composer\\Composer::upgradePHPUnit",
-        "drupal-phpunit-upgrade": "@composer update phpunit/phpunit symfony/phpunit-bridge phpspec/prophecy symfony/yaml --with-dependencies --no-progress",
+        "drupal-phpunit-upgrade": [
+            "@composer update phpunit/phpunit --with-dependencies --no-progress --ignore-platform-reqs",
+            "@composer require phpspec/prophecy-phpunit:^2 --no-progress --no-suggest --ignore-platform-reqs"
+        ],
         "post-update-cmd": [
             "Drupal\\Composer\\Composer::generateMetapackages"
         ],
diff --git a/composer.lock b/composer.lock
index 11b5e08089..2e8eacede9 100644
--- a/composer.lock
+++ b/composer.lock
@@ -486,7 +486,7 @@
             "dist": {
                 "type": "path",
                 "url": "core",
-                "reference": "5bd6798a64831fa08a343a14a0ee47127c4cb99f"
+                "reference": "568e11b75180f79954b390e34e79aff5a08246e5"
             },
             "require": {
                 "asm89/stack-cors": "^1.1",
@@ -529,7 +529,7 @@
                 "symfony/translation": "^4.4",
                 "symfony/validator": "^4.4",
                 "symfony/yaml": "^4.4",
-                "twig/twig": "^2.12.0",
+                "twig/twig": "^2.13.0",
                 "typo3/phar-stream-wrapper": "^3.1.3"
             },
             "conflict": {
@@ -709,6 +709,9 @@
                     "lib/Drupal/Core/DrupalKernelInterface.php",
                     "lib/Drupal/Core/Installer/InstallerRedirectTrait.php",
                     "lib/Drupal/Core/Site/Settings.php"
+                ],
+                "files": [
+                    "includes/class_aliases.php"
                 ]
             },
             "scripts": {
diff --git a/core/.cspell.json b/core/.cspell.json
index ee5bc110ca..64c36e2fe6 100644
--- a/core/.cspell.json
+++ b/core/.cspell.json
@@ -9,6 +9,7 @@
       "lib/Drupal/Component/Diff/**",
       "lib/Drupal/Component/Transliteration/data/**",
       "lib/Drupal/Core/File/MimeType/ExtensionMimeTypeGuesser.php",
+      "lib/Drupal/Core/Php8/**",
       "modules/**/Migrate*Test.php",
       "modules/color/preview.html",
       "modules/color/tests/modules/color_test/themes/color_test_theme/color/preview.html",
diff --git a/core/composer.json b/core/composer.json
index cf64c7800f..6691ec372c 100644
--- a/core/composer.json
+++ b/core/composer.json
@@ -31,7 +31,7 @@
         "symfony/polyfill-iconv": "^1.0",
         "symfony/yaml": "^4.4",
         "typo3/phar-stream-wrapper": "^3.1.3",
-        "twig/twig": "^2.12.0",
+        "twig/twig": "^2.13.0",
         "doctrine/reflection": "^1.1",
         "doctrine/annotations": "^1.4",
         "guzzlehttp/guzzle": "^6.5.2",
@@ -196,7 +196,8 @@
             "lib/Drupal/Core/DrupalKernelInterface.php",
             "lib/Drupal/Core/Installer/InstallerRedirectTrait.php",
             "lib/Drupal/Core/Site/Settings.php"
-        ]
+        ],
+        "files": [ "includes/class_aliases.php" ]
     },
     "config": {
         "preferred-install": "dist"