diff --git a/.github/patch-types.php b/.github/patch-types.php
index 5c68a66c89c79..46c6980dab4a2 100644
--- a/.github/patch-types.php
+++ b/.github/patch-types.php
@@ -33,6 +33,7 @@
         case false !== strpos($file, '/src/Symfony/Component/DependencyInjection/Tests/Fixtures/includes/autowiring_classes.php'):
         case false !== strpos($file, '/src/Symfony/Component/DependencyInjection/Tests/Fixtures/includes/uniontype_classes.php'):
         case false !== strpos($file, '/src/Symfony/Component/DependencyInjection/Tests/Fixtures/ParentNotExists.php'):
+        case false !== strpos($file, '/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/'):
         case false !== strpos($file, '/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Prototype/BadClasses/MissingParent.php'):
         case false !== strpos($file, '/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/'):
         case false !== strpos($file, '/src/Symfony/Component/ErrorHandler/Tests/Fixtures/'):
diff --git a/src/Symfony/Component/DependencyInjection/Dumper/Preloader.php b/src/Symfony/Component/DependencyInjection/Dumper/Preloader.php
index fb39645022edf..1e0b6919fd1fe 100644
--- a/src/Symfony/Component/DependencyInjection/Dumper/Preloader.php
+++ b/src/Symfony/Component/DependencyInjection/Dumper/Preloader.php
@@ -94,7 +94,7 @@ private static function doPreload(string $class, array &$preloaded): void
 
     private static function preloadType(?\ReflectionType $t, array &$preloaded): void
     {
-        if (!$t || $t->isBuiltin()) {
+        if (!$t) {
             return;
         }
 
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Dumper/PreloaderTest.php b/src/Symfony/Component/DependencyInjection/Tests/Dumper/PreloaderTest.php
new file mode 100644
index 0000000000000..a9b3242031537
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Dumper/PreloaderTest.php
@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\DependencyInjection\Tests\Dumper;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\DependencyInjection\Dumper\Preloader;
+
+class PreloaderTest extends TestCase
+{
+    /**
+     * @requires PHP 7.4
+     */
+    public function testPreload()
+    {
+        $r = new \ReflectionMethod(Preloader::class, 'doPreload');
+        $r->setAccessible(true);
+
+        $preloaded = [];
+
+        $r->invokeArgs(null, ['Symfony\Component\DependencyInjection\Tests\Fixtures\Preload\Dummy', &$preloaded]);
+
+        self::assertTrue(class_exists('Symfony\Component\DependencyInjection\Tests\Fixtures\Preload\Dummy', false));
+        self::assertTrue(class_exists('Symfony\Component\DependencyInjection\Tests\Fixtures\Preload\A', false));
+        self::assertTrue(class_exists('Symfony\Component\DependencyInjection\Tests\Fixtures\Preload\B', false));
+        self::assertTrue(class_exists('Symfony\Component\DependencyInjection\Tests\Fixtures\Preload\C', false));
+    }
+
+    /**
+     * @requires PHP 8
+     */
+    public function testPreloadUnion()
+    {
+        $r = new \ReflectionMethod(Preloader::class, 'doPreload');
+        $r->setAccessible(true);
+
+        $preloaded = [];
+
+        $r->invokeArgs(null, ['Symfony\Component\DependencyInjection\Tests\Fixtures\Preload\UnionDummy', &$preloaded]);
+
+        self::assertTrue(class_exists('Symfony\Component\DependencyInjection\Tests\Fixtures\Preload\UnionDummy', false));
+        self::assertTrue(class_exists('Symfony\Component\DependencyInjection\Tests\Fixtures\Preload\D', false));
+        self::assertTrue(class_exists('Symfony\Component\DependencyInjection\Tests\Fixtures\Preload\E', false));
+    }
+}
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/A.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/A.php
new file mode 100644
index 0000000000000..2802a577e85b1
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/A.php
@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\DependencyInjection\Tests\Fixtures\Preload;
+
+final class A
+{
+}
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/B.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/B.php
new file mode 100644
index 0000000000000..66dda101ce436
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/B.php
@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\DependencyInjection\Tests\Fixtures\Preload;
+
+final class B
+{
+}
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/C.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/C.php
new file mode 100644
index 0000000000000..331e9fed19c95
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/C.php
@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\DependencyInjection\Tests\Fixtures\Preload;
+
+final class C
+{
+}
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/D.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/D.php
new file mode 100644
index 0000000000000..52e10e918149b
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/D.php
@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\DependencyInjection\Tests\Fixtures\Preload;
+
+final class D
+{
+}
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/Dummy.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/Dummy.php
new file mode 100644
index 0000000000000..35d61be5a573c
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/Dummy.php
@@ -0,0 +1,30 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\DependencyInjection\Tests\Fixtures\Preload;
+
+final class Dummy
+{
+    public A $a;
+
+    public function doSomething(B $b): ?C
+    {
+        return null;
+    }
+
+    public function noTypes($foo)
+    {
+    }
+
+    public function builtinTypes(int $foo): ?string
+    {
+    }
+}
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/E.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/E.php
new file mode 100644
index 0000000000000..b4ec3b2734c57
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/E.php
@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\DependencyInjection\Tests\Fixtures\Preload;
+
+final class E
+{
+}
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/UnionDummy.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/UnionDummy.php
new file mode 100644
index 0000000000000..24b709b0a2d69
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Preload/UnionDummy.php
@@ -0,0 +1,21 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\DependencyInjection\Tests\Fixtures\Preload;
+
+final class UnionDummy
+{
+    public D|E $de;
+
+    public function builtinTypes(int|float $foo): string|\Stringable|null
+    {
+    }
+}

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