diff --git a/src/Symfony/Component/HttpFoundation/BinaryFileResponse.php b/src/Symfony/Component/HttpFoundation/BinaryFileResponse.php
index aa212a3ca9d2..c20b31f3de35 100644
--- a/src/Symfony/Component/HttpFoundation/BinaryFileResponse.php
+++ b/src/Symfony/Component/HttpFoundation/BinaryFileResponse.php
@@ -218,6 +218,7 @@ public function prepare(Request $request)
 
                 $this->setStatusCode(206);
                 $this->headers->set('Content-Range', sprintf('bytes %s-%s/%s', $start, $end, $fileSize));
+                $this->headers->set('Content-Length', $end - $start + 1);
             }
         }