diff --git a/includes/bootstrap.inc b/includes/bootstrap.inc
index bc5d5a3..6905ba5 100644
--- a/includes/bootstrap.inc
+++ b/includes/bootstrap.inc
@@ -2541,7 +2541,7 @@ function drupal_language_initialize() {
   }
 
   // Send appropriate HTTP-Header for browsers and search engines.
-  header('Content-Language: ' . $language->language);
+  drupal_add_http_header('Content-Language', $language->language);
 }
 
 /**