diff --git a/CHANGELOG.md b/CHANGELOG.md
index 558dc72..f0296ba 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@
 * feat(`Context`): `with()` not accepts multiple argument.
 * build: Deinternalize `ObjectCacheFactory`
 * fix(`PresetMapping`): Support proxied classes, add tests.
+* fix: Disallow proxy for objects with dynamic properties, including `stdClass`.
 
 ## 1.0.0
 
diff --git a/config/services.php b/config/services.php
index e07de6c..000ef65 100644
--- a/config/services.php
+++ b/config/services.php
@@ -28,6 +28,7 @@
 use Rekalogika\Mapper\Mapping\MappingFactoryInterface;
 use Rekalogika\Mapper\ObjectCache\Implementation\ObjectCacheFactory;
 use Rekalogika\Mapper\Proxy\Implementation\DoctrineProxyGenerator;
+use Rekalogika\Mapper\Proxy\Implementation\DynamicPropertiesProxyGenerator;
 use Rekalogika\Mapper\Proxy\Implementation\ProxyFactory;
 use Rekalogika\Mapper\Proxy\Implementation\ProxyGenerator;
 use Rekalogika\Mapper\Proxy\Implementation\ProxyRegistry;
@@ -406,6 +407,13 @@
             service('doctrine'),
         ]);
 
+    $services
+        ->set('rekalogika.mapper.proxy.generator.dynamic_properties', DynamicPropertiesProxyGenerator::class)
+        ->decorate('rekalogika.mapper.proxy.generator')
+        ->args([
+            service('.inner'),
+        ]);
+
     # proxy registry
 
     $services
diff --git a/src/Proxy/Implementation/DynamicPropertiesProxyGenerator.php b/src/Proxy/Implementation/DynamicPropertiesProxyGenerator.php
new file mode 100644
index 0000000..82ab81e
--- /dev/null
+++ b/src/Proxy/Implementation/DynamicPropertiesProxyGenerator.php
@@ -0,0 +1,44 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of rekalogika/mapper package.
+ *
+ * (c) Priyadi Iman Nurcahyo <https://rekalogika.dev>
+ *
+ * For the full copyright and license information, please view the LICENSE file
+ * that was distributed with this source code.
+ */
+
+namespace Rekalogika\Mapper\Proxy\Implementation;
+
+use Rekalogika\Mapper\Proxy\Exception\ProxyNotSupportedException;
+use Rekalogika\Mapper\Proxy\ProxyGeneratorInterface;
+
+/**
+ * Prevent proxy creation for objects with dynamic properties.
+ *
+ * @internal
+ */
+final readonly class DynamicPropertiesProxyGenerator implements ProxyGeneratorInterface
+{
+    public function __construct(
+        private ProxyGeneratorInterface $decorated,
+    ) {
+    }
+
+    public function generateProxyCode(string $realClass, string $proxyClass): string
+    {
+        $reflection = new \ReflectionClass($realClass);
+
+        do {
+            if ($reflection->getAttributes(\AllowDynamicProperties::class)) {
+                throw new ProxyNotSupportedException($realClass, reason: 'Objects with dynamic properties do not support proxying.');
+            }
+        } while ($reflection = $reflection->getParentClass());
+
+
+        return $this->decorated->generateProxyCode($realClass, $proxyClass);
+    }
+}