diff --git a/.github/patch-types.php b/.github/patch-types.php
index 311e9e7ee4..d3dfc9073d 100644
--- a/.github/patch-types.php
+++ b/.github/patch-types.php
@@ -30,6 +30,7 @@ foreach ($loader->getClassMap() as $class => $file) {
         case false !== strpos($file, '/src/Symfony/Component/Config/Tests/Fixtures/ParseError.php'):
         case false !== strpos($file, '/src/Symfony/Component/Debug/Tests/Fixtures/'):
         case false !== strpos($file, '/src/Symfony/Component/DependencyInjection/Tests/Compiler/OptionalServiceClass.php'):
+        case false !== strpos($file, '/src/Symfony/Component/DependencyInjection/Tests/Fixtures/CheckTypeDeclarationsPass/UnionConstructor.php'):
         case false !== strpos($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'):
diff --git a/src/Symfony/Component/DependencyInjection/Compiler/CheckTypeDeclarationsPass.php b/src/Symfony/Component/DependencyInjection/Compiler/CheckTypeDeclarationsPass.php
index ae1a2ec204..752633ce17 100644
--- a/src/Symfony/Component/DependencyInjection/Compiler/CheckTypeDeclarationsPass.php
+++ b/src/Symfony/Component/DependencyInjection/Compiler/CheckTypeDeclarationsPass.php
@@ -153,26 +153,27 @@ final class CheckTypeDeclarationsPass extends AbstractRecursivePass
     /**
      * @throws InvalidParameterTypeException When a parameter is not compatible with the declared type
      */
-    private function checkType(Definition $checkedDefinition, $value, \ReflectionParameter $parameter, ?string $envPlaceholderUniquePrefix, string $type = null): void
+    private function checkType(Definition $checkedDefinition, $value, \ReflectionParameter $parameter, ?string $envPlaceholderUniquePrefix, \ReflectionType $reflectionType = null): void
     {
-        if (null === $type) {
-            $type = $parameter->getType();
+        $reflectionType = $reflectionType ?? $parameter->getType();
 
-            if ($type instanceof \ReflectionUnionType) {
-                foreach ($type->getTypes() as $type) {
-                    try {
-                        $this->checkType($checkedDefinition, $value, $parameter, $envPlaceholderUniquePrefix, $type);
+        if ($reflectionType instanceof \ReflectionUnionType) {
+            foreach ($reflectionType->getTypes() as $t) {
+                try {
+                    $this->checkType($checkedDefinition, $value, $parameter, $envPlaceholderUniquePrefix, $t);
 
-                        return;
-                    } catch (InvalidParameterTypeException $e) {
-                    }
+                    return;
+                } catch (InvalidParameterTypeException $e) {
                 }
-
-                throw new InvalidParameterTypeException($this->currentId, $e->getCode(), $parameter);
             }
 
-            $type = $type->getName();
+            throw new InvalidParameterTypeException($this->currentId, $e->getCode(), $parameter);
         }
+        if (!$reflectionType instanceof \ReflectionNamedType) {
+            return;
+        }
+
+        $type = $reflectionType->getName();
 
         if ($value instanceof Reference) {
             if (!$this->container->has($value = (string) $value)) {
@@ -285,7 +286,7 @@ final class CheckTypeDeclarationsPass extends AbstractRecursivePass
 
         $checkFunction = sprintf('is_%s', $type);
 
-        if (!$parameter->getType()->isBuiltin() || !$checkFunction($value)) {
+        if (!$reflectionType->isBuiltin() || !$checkFunction($value)) {
             throw new InvalidParameterTypeException($this->currentId, \is_object($value) ? $class : \gettype($value), $parameter);
         }
     }
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Compiler/CheckTypeDeclarationsPassTest.php b/src/Symfony/Component/DependencyInjection/Tests/Compiler/CheckTypeDeclarationsPassTest.php
index 0842f26879..c683c3ed0a 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Compiler/CheckTypeDeclarationsPassTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Compiler/CheckTypeDeclarationsPassTest.php
@@ -26,6 +26,7 @@ use Symfony\Component\DependencyInjection\Tests\Fixtures\CheckTypeDeclarationsPa
 use Symfony\Component\DependencyInjection\Tests\Fixtures\CheckTypeDeclarationsPass\BarOptionalArgumentNotNull;
 use Symfony\Component\DependencyInjection\Tests\Fixtures\CheckTypeDeclarationsPass\Foo;
 use Symfony\Component\DependencyInjection\Tests\Fixtures\CheckTypeDeclarationsPass\FooObject;
+use Symfony\Component\DependencyInjection\Tests\Fixtures\CheckTypeDeclarationsPass\UnionConstructor;
 use Symfony\Component\DependencyInjection\Tests\Fixtures\CheckTypeDeclarationsPass\Waldo;
 use Symfony\Component\DependencyInjection\Tests\Fixtures\CheckTypeDeclarationsPass\Wobble;
 use Symfony\Component\ExpressionLanguage\Expression;
@@ -803,4 +804,72 @@ class CheckTypeDeclarationsPassTest extends TestCase
 
         putenv('ARRAY=');
     }
+
+    /**
+     * @requires PHP 8
+     */
+    public function testUnionTypePassesWithReference()
+    {
+        $container = new ContainerBuilder();
+
+        $container->register('foo', Foo::class);
+        $container->register('union', UnionConstructor::class)
+            ->setArguments([new Reference('foo')]);
+
+        (new CheckTypeDeclarationsPass(true))->process($container);
+
+        $this->addToAssertionCount(1);
+    }
+
+    /**
+     * @requires PHP 8
+     */
+    public function testUnionTypePassesWithBuiltin()
+    {
+        $container = new ContainerBuilder();
+
+        $container->register('union', UnionConstructor::class)
+            ->setArguments([42]);
+
+        (new CheckTypeDeclarationsPass(true))->process($container);
+
+        $this->addToAssertionCount(1);
+    }
+
+    /**
+     * @requires PHP 8
+     */
+    public function testUnionTypeFailsWithReference()
+    {
+        $container = new ContainerBuilder();
+
+        $container->register('waldo', Waldo::class);
+        $container->register('union', UnionConstructor::class)
+            ->setArguments([new Reference('waldo')]);
+
+        $this->expectException(\Symfony\Component\DependencyInjection\Exception\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Invalid definition for service "union": argument 1 of "Symfony\\Component\\DependencyInjection\\Tests\\Fixtures\\CheckTypeDeclarationsPass\\UnionConstructor::__construct" accepts "Symfony\Component\DependencyInjection\Tests\Fixtures\CheckTypeDeclarationsPass\Foo|int", "Symfony\Component\DependencyInjection\Tests\Fixtures\CheckTypeDeclarationsPass\Waldo" passed.');
+
+        (new CheckTypeDeclarationsPass(true))->process($container);
+
+        $this->addToAssertionCount(1);
+    }
+
+    /**
+     * @requires PHP 8
+     */
+    public function testUnionTypeFailsWithBuiltin()
+    {
+        $container = new ContainerBuilder();
+
+        $container->register('union', UnionConstructor::class)
+            ->setArguments([[1, 2, 3]]);
+
+        $this->expectException(\Symfony\Component\DependencyInjection\Exception\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Invalid definition for service "union": argument 1 of "Symfony\\Component\\DependencyInjection\\Tests\\Fixtures\\CheckTypeDeclarationsPass\\UnionConstructor::__construct" accepts "Symfony\Component\DependencyInjection\Tests\Fixtures\CheckTypeDeclarationsPass\Foo|int", "array" passed.');
+
+        (new CheckTypeDeclarationsPass(true))->process($container);
+
+        $this->addToAssertionCount(1);
+    }
 }
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/CheckTypeDeclarationsPass/UnionConstructor.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/CheckTypeDeclarationsPass/UnionConstructor.php
new file mode 100644
index 0000000000..5ba5972863
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/CheckTypeDeclarationsPass/UnionConstructor.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Symfony\Component\DependencyInjection\Tests\Fixtures\CheckTypeDeclarationsPass;
+
+class UnionConstructor
+{
+    public function __construct(Foo|int $arg)
+    {
+    }
+}