diff --git a/src/Symfony/Component/HttpFoundation/Request.php b/src/Symfony/Component/HttpFoundation/Request.php
index 18b10101c4..bd16eac471 100644
--- a/src/Symfony/Component/HttpFoundation/Request.php
+++ b/src/Symfony/Component/HttpFoundation/Request.php
@@ -410,6 +410,10 @@ class Request
             $dup->attributes->set('_format', $this->get('_format'));
         }
 
+        if (!$dup->getRequestFormat(null)) {
+            $dup->setRequestFormat($format = $this->getRequestFormat(null));
+        }
+
         return $dup;
     }
 
diff --git a/src/Symfony/Component/HttpFoundation/Tests/RequestTest.php b/src/Symfony/Component/HttpFoundation/Tests/RequestTest.php
index 6bbaff9297..ce5a5ec3fc 100644
--- a/src/Symfony/Component/HttpFoundation/Tests/RequestTest.php
+++ b/src/Symfony/Component/HttpFoundation/Tests/RequestTest.php
@@ -284,6 +284,12 @@ class RequestTest extends \PHPUnit_Framework_TestCase
 
         $this->assertEquals('json', $dup->getRequestFormat());
         $this->assertEquals('json', $dup->attributes->get('_format'));
+
+        $request = new Request();
+        $request->setRequestFormat('xml');
+        $dup = $request->duplicate();
+
+        $this->assertEquals('xml', $dup->getRequestFormat());
     }
 
     /**