diff -u b/core/includes/module.inc b/core/includes/module.inc
--- b/core/includes/module.inc
+++ b/core/includes/module.inc
@@ -186,8 +186,9 @@
   system_list_reset();
   $module_file_list = state()->get('system.module_file_list');
   $theme_data = state()->get('system.themes');
-  // As themes do not need to be installed to be used during installation the
-  // state entry for system.themes might not exist. This will be resolved by
+  // As themes do not need to be installed to be used there is an issue during
+  // installation. The state entry for system.themes does not exist and we need
+  // theme data in order for installation to work. This will be resolved by
   // http://drupal.org/node/1067408.
   if (empty($theme_data)) {
     $theme_data = system_rebuild_theme_data(FALSE);
diff -u b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
--- b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
@@ -190,7 +190,7 @@
 
     // Load the first update screen.
     $update_url = $GLOBALS['base_url'] . '/core/update.php';
-    $this->drupal7Get($update_url);
+    $this->upgradeGet($update_url);
     if (!$this->assertResponse(200)) {
       throw new Exception('Initial GET to update.php did not return HTTP 200 status.');
     }
@@ -263,26 +263,22 @@
   }
 
   /**
-   * Retrieves a Drupal 7 absolute path.
+   * Retrieves a Drupal 7 absolute path for upgrade.
    *
    * This function does not call url() to prevent system_list() invocation
    * before key_value table exists.
    *
    * @param $path
    *   Drupal path or URL to load into internal browser
-   * @param $options
-   *   Options to be forwarded to url().
-   * @param $headers
-   *   An array containing additional HTTP request headers, each formatted as
-   *   "name: value".
+   *
    * @return
    *   The retrieved HTML string, also available as $this->drupalGetContent()
    */
-  protected function drupal7Get($path, array $options = array(), array $headers = array()) {
+  protected function upgradeGet($path) {
     // We re-using a CURL connection here. If that connection still has certain
     // options set, it might change the GET into a POST. Make sure we clear out
     // previous options.
-    $out = $this->curlExec(array(CURLOPT_HTTPGET => TRUE, CURLOPT_URL => $path, CURLOPT_NOBODY => FALSE, CURLOPT_HTTPHEADER => $headers));
+    $out = $this->curlExec(array(CURLOPT_HTTPGET => TRUE, CURLOPT_URL => $path, CURLOPT_NOBODY => FALSE));
     // Ensure that any changes to variables in the other thread are picked up.
     $this->refreshVariables();