diff --git a/core/includes/common.inc b/core/includes/common.inc
index a002e45..9aa2b84 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -3658,11 +3658,11 @@ function drupal_prepare_page($page) {
   // cache, even though they should be. This happens because they're rendered
   // directly by the theme system.
   // @todo Remove this once https://drupal.org/node/1869476 lands.
-  if (theme_get_setting('features.main_menu') && count(menu_main_menu())) {
+  if (!defined('MAINTENANCE_MODE') && theme_get_setting('features.main_menu') && count(menu_main_menu())) {
     $main_links_source = _menu_get_links_source('main_links', 'main');
     $page['page_top']['#cache']['tags']['menu'][$main_links_source] = $main_links_source;
   }
-  if (theme_get_setting('features.secondary_menu') && count(menu_secondary_menu())) {
+  if (!defined('MAINTENANCE_MODE') && theme_get_setting('features.secondary_menu') && count(menu_secondary_menu())) {
     $secondary_links_source = _menu_get_links_source('secondary_links', 'account');
     $page['page_top']['#cache']['tags']['menu'][$secondary_links_source] = $secondary_links_source;
   }
diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index de4069e..a97387c 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -9,7 +9,6 @@
 use Drupal\Core\Database\Database;
 use Drupal\Core\Database\DatabaseExceptionWrapper;
 use Drupal\Core\Database\Install\TaskException;
-use Drupal\Core\Extension\InfoParser;
 use Drupal\Core\Installer\Exception\AlreadyInstalledException;
 use Drupal\Core\Installer\Exception\InstallerException;
 use Drupal\Core\Installer\Exception\NoProfilesException;
@@ -301,7 +300,6 @@ function install_begin_request(&$install_state) {
   require_once __DIR__ . '/form.inc';
   require_once __DIR__ . '/batch.inc';
   require_once __DIR__ . '/ajax.inc';
-  require_once __DIR__ . '/menu.inc';
 
   // Load module basics (needed for hook invokes).
   include_once __DIR__ . '/module.inc';
@@ -347,46 +345,18 @@ function install_begin_request(&$install_state) {
     }
   }
 
-  // Add list of all available profiles to the installation state.
-  $listing = new ExtensionDiscovery();
-  $listing->setProfileDirectories(array());
-  $install_state['profiles'] += $listing->scan('profile');
-
-  // Prime drupal_get_filename()'s static cache.
-  foreach ($install_state['profiles'] as $name => $profile) {
-    drupal_get_filename('profile', $name, $profile->uri);
-  }
-
-  $container->set('info_parser', new InfoParser());
-  if ($profile = _install_select_profile($install_state)) {
-    $install_state['parameters']['profile'] = $profile;
-    install_load_profile($install_state);
-    if (isset($install_state['profile_info']['distribution']['install']['theme'])) {
-      $install_state['theme'] = $install_state['profile_info']['distribution']['install']['theme'];
-    }
-  }
-
   // Replace services with in-memory and null implementations. This kernel is
   // replaced with a regular one in drupal_install_system().
   if (!$install_state['base_system_verified']) {
+    $environment = 'install';
     $GLOBALS['conf']['container_service_providers']['InstallerServiceProvider'] = 'Drupal\Core\Installer\InstallerServiceProvider';
-    $kernel = new DrupalKernel('install', drupal_classloader(), FALSE);
-    $module_list['system'] = 'core/modules/system/system.module';
-    $kernel->updateModules($module_list, $module_list);
   }
   else {
-    $kernel = new DrupalKernel('prod', drupal_classloader(), FALSE);
+    $environment = 'prod';
   }
-  $kernel->boot();
 
-  // Override the module list with a minimal set of modules.
-  $module_handler = \Drupal::moduleHandler();
-  if ($profile && !$module_handler->moduleExists($profile)) {
-    $module_list = $module_handler->getModuleList();
-    $module_list[$profile] = $install_state['profiles'][$profile]->uri;
-    $module_handler->setModuleList($module_list);
-    $kernel->updateModules($module_list, $module_list);
-  }
+  $kernel = new DrupalKernel($environment, drupal_classloader(), FALSE);
+  $kernel->boot();
 
   // Enter the request scope and add the Request.
   // @todo Remove this after converting all installer screens into controllers.
@@ -410,7 +380,38 @@ function install_begin_request(&$install_state) {
     \Drupal::translation()->setDefaultLangcode($install_state['parameters']['langcode']);
   }
 
-  // _theme() requires all modules to be loaded.
+  // Add list of all available profiles to the installation state.
+  $listing = new ExtensionDiscovery();
+  $listing->setProfileDirectories(array());
+  $install_state['profiles'] += $listing->scan('profile');
+
+  // Prime drupal_get_filename()'s static cache.
+  foreach ($install_state['profiles'] as $name => $profile) {
+    drupal_get_filename('profile', $name, $profile->uri);
+  }
+
+  if ($profile = _install_select_profile($install_state)) {
+    $install_state['parameters']['profile'] = $profile;
+    install_load_profile($install_state);
+    if (isset($install_state['profile_info']['distribution']['install']['theme'])) {
+      $install_state['theme'] = $install_state['profile_info']['distribution']['install']['theme'];
+    }
+  }
+
+  // Override the module list with a minimal set of modules.
+  $module_handler = \Drupal::moduleHandler();
+  $module_list = $module_handler->getModuleList();
+  if (!$module_handler->moduleExists('system')) {
+    $module_list['system'] = 'core/modules/system/system.module';
+  }
+  if ($profile && !$module_handler->moduleExists($profile)) {
+    $module_list[$profile] = $install_state['profiles'][$profile]->uri;
+  }
+  $module_handler->setModuleList($module_list);
+  // After setting up a custom and finite module list in a custom low-level
+  // bootstrap like here, ensure to use ModuleHandler::loadAll() so that
+  // ModuleHandler::isLoaded() returns TRUE, since that is a condition being
+  // checked by other subsystems (e.g., the theme system).
   $module_handler->loadAll();
 
   // Prepare for themed output. We need to run this at the beginning of the
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index d1c13f9..fe511c7 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -2079,17 +2079,25 @@ function template_preprocess_page(&$variables) {
 
   $variables['base_path']         = base_path();
   $variables['front_page']        = url();
-  $variables['feed_icons']        = drupal_get_feeds();
   $variables['language']          = $language_interface;
   $variables['language']->dir     = $language_interface->direction ? 'rtl' : 'ltr';
   $variables['logo']              = theme_get_setting('logo.url');
-  $variables['main_menu']         = theme_get_setting('features.main_menu') ? menu_main_menu() : array();
-  $variables['secondary_menu']    = theme_get_setting('features.secondary_menu') ? menu_secondary_menu() : array();
   $variables['site_name']         = (theme_get_setting('features.name') ? String::checkPlain($site_config->get('name')) : '');
   $variables['site_slogan']       = (theme_get_setting('features.slogan') ? filter_xss_admin($site_config->get('slogan')) : '');
+
   if (!defined('MAINTENANCE_MODE')) {
-    $variables['tabs']              = menu_local_tabs();
-    $variables['action_links']      = menu_get_local_actions();
+    $variables['main_menu']      = theme_get_setting('features.main_menu') ? menu_main_menu() : array();
+    $variables['secondary_menu'] = theme_get_setting('features.secondary_menu') ? menu_secondary_menu() : array();
+    $variables['tabs']           = menu_local_tabs();
+    $variables['action_links']   = menu_get_local_actions();
+    $variables['feed_icons']     = drupal_get_feeds();
+  }
+  else {
+    $variables['main_menu']      = array();
+    $variables['secondary_menu'] = array();
+    $variables['tabs']           = array();
+    $variables['action_links']   = array();
+    $variables['feed_icons']     = '';
   }
 
   // Pass the main menu and secondary menu to the template as render arrays.