diff --git a/modules/simpletest/tests/common.test b/modules/simpletest/tests/common.test
index b3fc849..86e48ba 100644
--- a/modules/simpletest/tests/common.test
+++ b/modules/simpletest/tests/common.test
@@ -938,7 +938,7 @@ class DrupalHTTPRequestTestCase extends DrupalWebTestCase {
   }
 
   function setUp() {
-    parent::setUp('system_test');
+    parent::setUp('system_test', 'locale');
   }
 
   function testDrupalHTTPRequest() {
@@ -1035,6 +1035,22 @@ class DrupalHTTPRequestTestCase extends DrupalWebTestCase {
     $multiple_redirect_3 = drupal_http_request(url('system-test/multiple-redirects/3', array('absolute' => TRUE)), array('max_redirects' => 3));
     $this->assertEqual($multiple_redirect_3->redirect_url, $multiple_redirect_final_url, t('redirect_url contains the final redirection location after 3 redirects.'));
   }
+
+  /**
+   * Tests Content-language headers generated by Drupal.
+   */
+  function testDrupalHTTPRequestHeaders() {
+    // Check the default header.
+    $request = drupal_http_request(url('<front>', array('absolute' => TRUE)));
+    $this->assertEqual($request->headers['content-language'], 'en', t('Content-Language HTTP header is English.'));
+
+    // Add French language.
+    locale_add_language('fr', 'French');
+
+    // Request front page in French and check for matching Content-language.
+    $request = drupal_http_request(url('<front>', array('absolute' => TRUE, 'language' => $language)));
+    $this->assertEqual($request->headers['content-language'], 'fr', t('Content-Language HTTP header is French.'));
+  }
 }
 
 /**