diff --git a/Slim/Http/Response.php b/Slim/Http/Response.php
index <HASH>..<HASH> 100644
--- a/Slim/Http/Response.php
+++ b/Slim/Http/Response.php
@@ -134,7 +134,7 @@ class Response implements \ArrayAccess, \Countable, \IteratorAggregate
     {
         $this->setStatus($status);
         $this->headers = new \Slim\Http\Headers(array('Content-Type' => 'text/html'));
-        $this->headers->add($headers);
+        $this->headers->replace($headers);
         $this->cookies = new \Slim\Http\Cookies();
         $this->write($body);
     }
diff --git a/tests/Helper/SetTest.php b/tests/Helper/SetTest.php
index <HASH>..<HASH> 100644
--- a/tests/Helper/SetTest.php
+++ b/tests/Helper/SetTest.php
@@ -61,7 +61,7 @@ class SetTest extends PHPUnit_Framework_TestCase
 
     public function testAdd()
     {
-        $this->bag->add(array(
+        $this->bag->replace(array(
             'abc' => '123',
             'foo' => 'bar'
         ));
Fix loose ends caused by change from Set::add to Set::replace