diff --git a/src/Symfony/Component/HttpFoundation/Response.php b/src/Symfony/Component/HttpFoundation/Response.php
index 6b6308e36c..a4ad0e66ae 100644
--- a/src/Symfony/Component/HttpFoundation/Response.php
+++ b/src/Symfony/Component/HttpFoundation/Response.php
@@ -344,8 +344,9 @@ class Response
 
         // headers
         foreach ($this->headers->allPreserveCase() as $name => $values) {
+            $replace = 0 === strcasecmp($name, 'Content-Type');
             foreach ($values as $value) {
-                header($name.': '.$value, false, $this->statusCode);
+                header($name.': '.$value, $replace, $this->statusCode);
             }
         }