diff --git a/docs/best-practices/controllers.md b/docs/best-practices/controllers.md
index 3744783..a4b95e5 100644
--- a/docs/best-practices/controllers.md
+++ b/docs/best-practices/controllers.md
@@ -190,8 +190,6 @@ covers most common use cases:
 * Each class may or may not have a constructor.
 * If the constructor has an optional argument, it will be omitted unless an
   explicit [container configuration](#container-configuration) is used.
-* If the constructor has a nullable argument, it will be given a `null` value
-  unless an explicit [container configuration](#container-configuration) is used.
 * If the constructor references another class, it will load this class next.
 
 This covers most common use cases where the request handler class uses a
@@ -325,27 +323,6 @@ some manual configuration like this:
     ]);
 
 
-    $app = new FrameworkX\App($container);
-
-    // …
-    ```
-
-=== "Nullable values"
-
-    ```php title="public/index.php"
-    <?php
-
-    require __DIR__ . '/../vendor/autoload.php';
-
-    $container = new FrameworkX\Container([
-        Acme\Todo\UserController::class => function (?string $name) {
-            // example UserController class uses $name, defaults to null if not set
-            return new Acme\Todo\UserController($name ?? 'ACME');
-        },
-        'name' => 'Demo'
-    ]);
-
-
     $app = new FrameworkX\App($container);
 
     // …
@@ -415,7 +392,7 @@ all uppercase in any factory function like this:
         // Framework X also uses environment variables internally.
         // You may explicitly configure this built-in functionality like this:
         // 'X_LISTEN' => '0.0.0.0:8081'
-        // 'X_LISTEN' => fn(?string $PORT = '8080') => '0.0.0.0:' . $PORT
+        // 'X_LISTEN' => fn(string $PORT = '8080') => '0.0.0.0:' . $PORT
         'X_LISTEN' => '127.0.0.1:8080'
     ]);
 
diff --git a/src/Container.php b/src/Container.php
index 387d4d5..01c7e14 100644
--- a/src/Container.php
+++ b/src/Container.php
@@ -296,9 +296,6 @@ private function loadParameter(\ReflectionParameter $parameter, int $depth, bool
             if ($parameter->isDefaultValueAvailable()) {
                 return $parameter->getDefaultValue();
             }
-            if ($type->allowsNull()) {
-                return null;
-            }
 
             throw new \Error(
                 self::parameterError($parameter, $for) . ' expects unsupported type ' . $type
@@ -321,14 +318,12 @@ private function loadParameter(\ReflectionParameter $parameter, int $depth, bool
             );
         }
 
-        // use default/nullable argument if not loadable as container variable or by type
-        if (!$type instanceof \ReflectionNamedType || $type->isBuiltin() || !\array_key_exists($type->getName(), $this->container)) {
-            if ($parameter->isDefaultValueAvailable()) {
-                return $parameter->getDefaultValue();
-            }
-            if ($type !== null && $type->allowsNull() && $type->getName() !== 'mixed') {
-                return null;
-            }
+        // use default argument if not loadable as container variable or by type
+        if (
+            $parameter->isDefaultValueAvailable() &&
+            (!$type instanceof \ReflectionNamedType || $type->isBuiltin() || !\array_key_exists($type->getName(), $this->container))
+        ) {
+            return $parameter->getDefaultValue();
         }
 
         // abort if required container variable is not defined or for any other primitive types (array etc.)
diff --git a/tests/ContainerTest.php b/tests/ContainerTest.php
index c63a130..c0db268 100644
--- a/tests/ContainerTest.php
+++ b/tests/ContainerTest.php
@@ -68,36 +68,6 @@ public function __invoke(ServerRequestInterface $request): Response
         $this->assertEquals('{"name":"Alice"}', (string) $response->getBody());
     }
 
-    public function testCallableReturnsCallableForNullableClassViaAutowiringWillDefaultToNullValue(): void
-    {
-        $request = new ServerRequest('GET', 'http://example.com/');
-
-        $controller = new class(new \stdClass()) {
-            /** @var ?\stdClass */
-            private $data;
-
-            public function __construct(?\stdClass $data)
-            {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
-            }
-        };
-
-        $container = new Container([]);
-
-        $callable = $container->callable(get_class($controller));
-        $this->assertInstanceOf(\Closure::class, $callable);
-
-        $response = $callable($request);
-        $this->assertInstanceOf(ResponseInterface::class, $response);
-        $this->assertEquals(200, $response->getStatusCode());
-        $this->assertEquals('null', (string) $response->getBody());
-    }
-
     public function testCallableReturnsCallableForNullableClassViaContainerConfiguration(): void
     {
         $request = new ServerRequest('GET', 'http://example.com/');
@@ -130,37 +100,6 @@ public function __invoke(ServerRequestInterface $request): Response
         $this->assertEquals('{}', (string) $response->getBody());
     }
 
-    /**
-     * @requires PHP 8
-     */
-    public function testCallableReturnsCallableForUnionWithNullViaAutowiringWillDefaultToNullValue(): void
-    {
-        $request = new ServerRequest('GET', 'http://example.com/');
-
-        // @phpstan-ignore-next-line for PHP < 8
-        $controller = new class(null) {
-            /** @var mixed */
-            private $data = false;
-
-            #[PHP8] public function __construct(string|int|null $data) { $this->data = $data; } // @phpstan-ignore-line
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
-            }
-        };
-
-        $container = new Container([]);
-
-        $callable = $container->callable(get_class($controller));
-        $this->assertInstanceOf(\Closure::class, $callable);
-
-        $response = $callable($request);
-        $this->assertInstanceOf(ResponseInterface::class, $response);
-        $this->assertEquals(200, $response->getStatusCode());
-        $this->assertEquals('null', (string) $response->getBody());
-    }
-
     public function testCallableReturnsCallableForClassWithNullDefaultViaAutowiringWillDefaultToNullValue(): void
     {
         $request = new ServerRequest('GET', 'http://example.com/');
@@ -843,7 +782,7 @@ public function __invoke(): ResponseInterface
             ResponseInterface::class => function (?\stdClass $user, ?\stdClass $data) {
                 return new Response(200, [], (string) json_encode(['user' => $user, 'data' => $data]));
             },
-            'user' => (object) []
+            'user' => (object) ['name' => 'Alice']
         ]);
 
         $callable = $container->callable(get_class($controller));
@@ -852,7 +791,7 @@ public function __invoke(): ResponseInterface
         $response = $callable($request);
         $this->assertInstanceOf(ResponseInterface::class, $response);
         $this->assertEquals(200, $response->getStatusCode());
-        $this->assertEquals('{"user":{},"data":null}', (string) $response->getBody());
+        $this->assertEquals('{"user":{"name":"Alice"},"data":{}}', (string) $response->getBody());
     }
 
     public function testCallableReturnsCallableForClassNameWithDependencyMappedWithFactoryThatRequiresNullableContainerVariablesWithFactory(): void
@@ -879,7 +818,7 @@ public function __invoke(): ResponseInterface
                 return new Response(200, [], (string) json_encode(['user' => $user, 'data' => $data]));
             },
             'user' => function (): ?\stdClass { // @phpstan-ignore-line
-                return (object) [];
+                return (object) ['name' => 'Alice'];
             }
         ]);
 
@@ -889,7 +828,7 @@ public function __invoke(): ResponseInterface
         $response = $callable($request);
         $this->assertInstanceOf(ResponseInterface::class, $response);
         $this->assertEquals(200, $response->getStatusCode());
-        $this->assertEquals('{"user":{},"data":null}', (string) $response->getBody());
+        $this->assertEquals('{"user":{"name":"Alice"},"data":{}}', (string) $response->getBody());
     }
 
     public function testCallableReturnsCallableForClassNameWithDependencyMappedWithFactoryThatRequiresContainerVariablesWithDefaultValues(): void
@@ -1153,40 +1092,6 @@ public function __invoke(): ResponseInterface
         $this->assertEquals('"bar"', (string) $response->getBody());
     }
 
-    public function testCallableReturnsCallableForClassNameWithDependencyMappedWithFactoryThatRequiresNullableStringEnvironmentVariableAssignsNull(): void
-    {
-        $request = new ServerRequest('GET', 'http://example.com/');
-
-        $controller = new class(new Response()) {
-            /** @var ResponseInterface */
-            private $response;
-
-            public function __construct(ResponseInterface $response)
-            {
-                $this->response = $response;
-            }
-
-            public function __invoke(): ResponseInterface
-            {
-                return $this->response;
-            }
-        };
-
-        $container = new Container([
-            ResponseInterface::class => function (?string $FOO) {
-                return new Response(200, [], (string) json_encode($FOO));
-            }
-        ]);
-
-        $callable = $container->callable(get_class($controller));
-        $this->assertInstanceOf(\Closure::class, $callable);
-
-        $response = $callable($request);
-        $this->assertInstanceOf(ResponseInterface::class, $response);
-        $this->assertEquals(200, $response->getStatusCode());
-        $this->assertEquals('null', (string) $response->getBody());
-    }
-
     public function testCallableReturnsCallableForClassNameWithDependencyMappedWithFactoryThatRequiresUntypedEnvironmentVariable(): void
     {
         $request = new ServerRequest('GET', 'http://example.com/');
@@ -1317,6 +1222,31 @@ public function __construct(\stdClass $data)
         $callable($request);
     }
 
+    public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesUnknownNullableVariable(): void
+    {
+        $request = new ServerRequest('GET', 'http://example.com/');
+
+        $controller = new class(new \stdClass()) {
+            public function __construct(\stdClass $data)
+            {
+                assert($data instanceof \stdClass);
+            }
+        };
+
+        $line = __LINE__ + 2;
+        $container = new Container([
+            \stdClass::class => function (?string $username) {
+                return (object) ['name' => $username];
+            }
+        ]);
+
+        $callable = $container->callable(get_class($controller));
+
+        $this->expectException(\Error::class);
+        $this->expectExceptionMessage('Argument #1 ($username) of {closure:' . __FILE__ . ':' . $line .'}() for stdClass requires container config with type ?string, none given');
+        $callable($request);
+    }
+
     public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesRecursiveVariable(): void
     {
         $request = new ServerRequest('GET', 'http://example.com/');
@@ -1973,6 +1903,82 @@ public function testGetEnvReturnsStringFromMapFactory(): void
         $this->assertEquals('bar', $container->getEnv('X_FOO'));
     }
 
+    /**
+     * @requires PHP 8
+     */
+    public function testGetEnvReturnsNullFromFactoryForUnsupportedUnionVariableWithNullDefaultEvenForKnownVariable(): void
+    {
+        $fn = null;
+        $fn = #[PHP8] function (string|int|null $bar = null) { return $bar; };
+        $container = new Container([
+            'X_FOO' => $fn,
+            'bar' => 'ignored'
+        ]);
+
+        $this->assertNull($container->getEnv('X_FOO'));
+    }
+
+    /**
+     * @requires PHP 8
+     */
+    public function testGetEnvReturnsStringFromFactoryForUnsupportedUnionVariableWithStringDefaultEvenForKnownVariable(): void
+    {
+        $fn = null;
+        $fn = #[PHP8] function (string|int|null $bar = 'default') { return $bar; };
+        $container = new Container([
+            'X_FOO' => $fn,
+            'bar' => 'ignored'
+        ]);
+
+        $this->assertEquals('default', $container->getEnv('X_FOO'));
+    }
+
+    public function testGetEnvReturnsNullFromFactoryForUnknownNullableVariableWithNullDefault(): void
+    {
+        $container = new Container([
+            'X_FOO' => function (?string $X_UNDEFINED = null) { return $X_UNDEFINED; }
+        ]);
+
+        $this->assertNull($container->getEnv('X_FOO'));
+    }
+
+    public function testGetEnvReturnsStringFromFactoryForUnknownVariableWithStringDefault(): void
+    {
+        $container = new Container([
+            'X_FOO' => function (string $X_UNDEFINED = 'foo') { return $X_UNDEFINED; }
+        ]);
+
+        $this->assertEquals('foo', $container->getEnv('X_FOO'));
+    }
+
+    /**
+     * @requires PHP 8
+     */
+    public function testGetEnvReturnsNullFromFactoryForUnknownAndUnsupportedUnionVariableWithNullDefault(): void
+    {
+        $fn = null;
+        $fn = #[PHP8] function (string|int|null $X_UNDEFINED = null) { return $X_UNDEFINED; };
+        $container = new Container([
+            'X_FOO' => $fn
+        ]);
+
+        $this->assertNull($container->getEnv('X_FOO'));
+    }
+
+    /**
+     * @requires PHP 8
+     */
+    public function testGetEnvReturnsStringFromFactoryForUnknownAndUnsupportedUnionVariableWithStringDefault(): void
+    {
+        $fn = null;
+        $fn = #[PHP8] function (string|int|null $X_UNDEFINED = 'default') { return $X_UNDEFINED; };
+        $container = new Container([
+            'X_FOO' => $fn
+        ]);
+
+        $this->assertEquals('default', $container->getEnv('X_FOO'));
+    }
+
     public function testGetEnvReturnsStringFromGlobalEnvIfNotSetInMap(): void
     {
         $container = new Container([]);
@@ -2233,6 +2239,33 @@ public function testGetEnvThrowsWhenFactoryFunctionExpectsRequiredEnvVariableBut
         $container->getEnv('X_FOO');
     }
 
+    public function testGetEnvThrowsWhenFactoryFunctionExpectsRequiredNullableEnvVariableButNoneGiven(): void
+    {
+        $line = __LINE__ + 2;
+        $container = new Container([
+            'X_FOO' => function (?string $X_UNDEFINED) { return $X_UNDEFINED; }
+        ]);
+
+        $this->expectException(\Error::class);
+        $this->expectExceptionMessage('Argument #1 ($X_UNDEFINED) of {closure:' . __FILE__ . ':' . $line . '}() for $X_FOO requires container config with type ?string, none given');
+        $container->getEnv('X_FOO');
+    }
+
+    /**
+     * @requires PHP 8
+     */
+    public function testGetEnvThrowsWhenFactoryFunctionExpectsRequiredMixedEnvVariableButNoneGiven(): void
+    {
+        $line = __LINE__ + 2;
+        $container = new Container([
+            'X_FOO' => function (mixed $X_UNDEFINED) { return $X_UNDEFINED; }
+        ]);
+
+        $this->expectException(\Error::class);
+        $this->expectExceptionMessage('Argument #1 ($X_UNDEFINED) of {closure:' . __FILE__ . ':' . $line . '}() for $X_FOO requires container config with type mixed, none given');
+        $container->getEnv('X_FOO');
+    }
+
     public function testGetEnvThrowsWhenFactoryFunctionExpectsNullableIntArgumentButGivenString(): void
     {
         $line = __LINE__ + 2;
@@ -2264,6 +2297,23 @@ public function testGetEnvThrowsWhenFactoryFunctionExpectsUnsupportedUnionType()
         $container->getEnv('X_FOO');
     }
 
+    /**
+     * @requires PHP 8
+     */
+    public function testGetEnvThrowsWhenFactoryFunctionExpectsNullableUnionType(): void
+    {
+        $line = __LINE__ + 2;
+        $fn = null;
+        $fn = #[PHP8] function (string|int|null $X_UNDEFINED) { return $X_UNDEFINED; };
+        $container = new Container([
+            'X_FOO' => $fn
+        ]);
+
+        $this->expectException(\Error::class);
+        $this->expectExceptionMessage('Argument #1 ($X_UNDEFINED) of {closure:' . __FILE__ . ':' . $line . '}() for $X_FOO expects unsupported type string|int|null');
+        $container->getEnv('X_FOO');
+    }
+
     /** @link https://3v4l.org/VaFMd */
     public function testGetEnvThrowsWhenFactoryFunctionExpectsIntArgumentButGivenAnonymousClass(): void
     {
diff --git a/tests/Io/RouteHandlerTest.php b/tests/Io/RouteHandlerTest.php
index a89fc79..69a3893 100644
--- a/tests/Io/RouteHandlerTest.php
+++ b/tests/Io/RouteHandlerTest.php
@@ -234,33 +234,6 @@ public function __invoke(): ?Response
         $this->assertSame($response, $ret);
     }
 
-    public function testHandleRequestWithGetRequestReturnsResponseFromMatchingHandlerClassNameWithNullableConstructor(): void
-    {
-        $request = new ServerRequest('GET', 'http://example.com/');
-        $response = new Response(200, [], '');
-
-        $controller = new class(null) {
-            /** @var ?Response */
-            public static $response;
-            public function __construct(?int $value)
-            {
-                assert($value === null);
-            }
-            public function __invoke(): ?Response
-            {
-                return self::$response;
-            }
-        };
-        $controller::$response = $response;
-
-        $handler = new RouteHandler();
-        $handler->map(['GET'], '/', get_class($controller));
-
-        $ret = $handler($request);
-
-        $this->assertSame($response, $ret);
-    }
-
     public function testHandleRequestWithGetRequestReturnsResponseFromMatchingHandlerClassNameWithRequiredResponseInConstructor(): void
     {
         $request = new ServerRequest('GET', 'http://example.com/');