ignore proxy object if not in hierarchy

src/EventDispatcher/Subscriber/DoctrineProxySubscriber.php

@@ -37,10 +37,9 @@ public function onPreSerialize(PreSerializeEvent $event): void
         $object = $event->getObject();
         $type = $event->getType();
 
-        // If the set type name is not an actual class, but a faked type for which a custom handler exists, we do not
-        // modify it with this subscriber. Also, we forgo autoloading here as an instance of this type is already created,
-        // so it must be loaded if its a real class.
-        $virtualType = !class_exists($type['name'], false);
+        // If the set type name is not an actual class, but a faked type for which a custom handler exists or
+        // object is not an instance of that class we do not modify it with this subscriber.
+        $virtualType = !class_exists($type['name']) || !$object instanceof $type['name'];
 
         if (
             $object instanceof PersistentCollection
@@ -85,12 +84,13 @@ public function onPreSerialize(PreSerializeEvent $event): void
     public function onPreSerializeTypedProxy(PreSerializeEvent $event, string $eventName, string $class, string $format, EventDispatcherInterface $dispatcher): void
     {
         $type = $event->getType();
-        // is a virtual type? then there is no need to change the event name
-        if (!class_exists($type['name'], false)) {
+        $object = $event->getObject();
+
+        // is a virtual type or not an instance of? then there is no need to change the event name
+        if (!class_exists($type['name']) || !$object instanceof $type['name']) {
             return;
         }
 
-        $object = $event->getObject();
         if ($object instanceof Proxy) {
             $parentClassName = get_parent_class($object);
 

tests/Serializer/EventDispatcher/Subscriber/DoctrineProxySubscriberTest.php

@@ -76,6 +76,17 @@ public function testProxyLoadingCanBeSkippedForVirtualTypes()
         self::assertFalse($obj->__isInitialized());
     }
 
+    public function testProxyLoadingCanBeSkippedForClassNotInHierarchy()
+    {
+        $subscriber = new DoctrineProxySubscriber(true);
+
+        $event = $this->createEvent($obj = new SimpleObjectProxy('a', 'b'), ['name' => 'stdClass', 'params' => []]);
+        $subscriber->onPreSerialize($event);
+
+        self::assertEquals(['name' => 'stdClass', 'params' => []], $event->getType());
+        self::assertFalse($obj->__isInitialized());
+    }
+
     public function testProxyLoadingCanBeSkippedByExclusionStrategy()
     {
         $subscriber = new DoctrineProxySubscriber(false, false);