diff --git a/src/Symfony/EventListener/ErrorListener.php b/src/Symfony/EventListener/ErrorListener.php
index c0eab7879dc..011f886c57f 100644
--- a/src/Symfony/EventListener/ErrorListener.php
+++ b/src/Symfony/EventListener/ErrorListener.php
@@ -80,9 +80,11 @@ protected function duplicateRequest(\Throwable $exception, Request $request): Re
 
         // Let the error handler take this we don't handle HTML nor non-api platform requests
         if (false === ($apiOperation?->getExtraProperties()['_api_error_handler'] ?? true) || 'html' === $format) {
-            $this->controller = 'error_controller';
+            $dup = parent::duplicateRequest($exception, $request);
+            // Override parent's `_controller` attribute without mutating $this->controller (worker-mode safety).
+            $dup->attributes->set('_controller', 'error_controller');
 
-            return parent::duplicateRequest($exception, $request);
+            return $dup;
         }
 
         if ($this->debug) {
@@ -90,6 +92,7 @@ protected function duplicateRequest(\Throwable $exception, Request $request): Re
         }
 
         $dup = parent::duplicateRequest($exception, $request);
+
         $operation = $this->initializeExceptionOperation($request, $exception, $format, $apiOperation);
 
         if (null === $operation->getProvider()) {
diff --git a/src/Symfony/Tests/EventListener/ErrorListenerTest.php b/src/Symfony/Tests/EventListener/ErrorListenerTest.php
index 09b8a990248..effa85bb103 100644
--- a/src/Symfony/Tests/EventListener/ErrorListenerTest.php
+++ b/src/Symfony/Tests/EventListener/ErrorListenerTest.php
@@ -142,4 +142,26 @@ public function testDuplicateExceptionWithErrorResource(): void
         $errorListener = new ErrorListener('action', null, true, [], $resourceMetadataCollectionFactory, ['jsonld' => ['application/ld+json']], [], $identifiersExtractor, $resourceClassResolver);
         $errorListener->onKernelException($exceptionEvent);
     }
+
+    public function testStateIsNeverModified(): void
+    {
+        $resourceClassResolver = $this->createStub(ResourceClassResolverInterface::class);
+        $kernel = $this->createStub(KernelInterface::class);
+        $kernel->method('handle')->willReturn(new Response());
+
+        $request = Request::create('/');
+        $request->headers->set('Accept', 'text/html');
+        $exception = new \Exception();
+        $exceptionEvent = new ExceptionEvent($kernel, $request, HttpKernelInterface::SUB_REQUEST, $exception);
+
+        $initialController = 'initial_controller';
+        $errorListener = new ErrorListener($initialController, null, false, [], null, ['jsonproblem' => ['application/problem+json']], [], null, $resourceClassResolver);
+
+        $errorListener->onKernelException($exceptionEvent);
+
+        $refl = new \ReflectionClass($errorListener);
+        $controllerProp = $refl->getProperty('controller');
+
+        $this->assertEquals($initialController, $controllerProp->getValue($errorListener), 'The controller property must never be modified.');
+    }
 }