diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 080fe8c..a7e4660 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1390,49 +1390,6 @@ function theme_get_suggestions($args, $base, $delimiter = '__') {
 }
 
 /**
- * Prepares variables for maintenance page templates.
- *
- * Default template: maintenance-page.html.twig.
- *
- * @param array $variables
- *   An associative array containing:
- *   - content - An array of page content.
- *
- * @see system_page_attachments()
- */
-function template_preprocess_page__maintenance(&$variables) {
-
-  // @see system_page_attachments()
-  $variables['#attached']['library'][] = 'system/maintenance';
-
-  // Maintenance page and install page need branding info in variables because
-  // there is no blocks.
-  $site_config = \Drupal::config('system.site');
-  $variables['logo'] = theme_get_setting('logo.url');
-  $variables['site_name'] = $site_config->get('name');
-  $variables['site_slogan'] = $site_config->get('slogan');
-}
-
-/**
- * Prepares variables for install page templates.
- *
- * Default template: install-page.html.twig.
- *
- * @param array $variables
- *   An associative array containing:
- *   - content - An array of page content.
- *
- * @see template_preprocess_page__maintenance()
- */
-function template_preprocess_page__maintenance__install(&$variables) {
-
-  // Override the site name that is displayed on the page, since Drupal is
-  // still in the process of being installed.
-  $distribution_name = drupal_install_profile_distribution_name();
-  $variables['site_name'] = $distribution_name;
-}
-
-/**
  * Prepares variables for region templates.
  *
  * Default template: region.html.twig.
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index a8cc12d..3a22a9f 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -253,39 +253,71 @@ function system_theme_suggestions_html(array $variables) {
  * Implements hook_theme_suggestions_HOOK().
  */
 function system_theme_suggestions_page(array $variables) {
-  if (\Drupal::service('path.matcher')->isFrontPage()) {
-    $path_args = [''];
-  }
-  else {
-    $path_args = explode('/', Url::fromRoute('<current>')->getInternalPath());
-  }
-  return theme_get_suggestions($path_args, 'page');
-}
-
-/**
- * Implements hook_theme_suggestions_HOOK().
- */
-function system_theme_suggestions_maintenance_page(array $variables) {
-  $suggestions = array();
-
   // Dead databases will show error messages so supplying this template will
   // allow themers to override the page and the content completely.
-  $offline = defined('MAINTENANCE_MODE');
   try {
-    \Drupal::service('path.matcher')->isFrontPage();
+    if (\Drupal::service('path.matcher')->isFrontPage()) {
+      $path_args = [''];
+    }
+    else {
+      $path_args = explode('/', Url::fromRoute('<current>')->getInternalPath());
+    }
+    return theme_get_suggestions($path_args, 'page');
   }
   catch (Exception $e) {
     // The database is not yet available.
     $offline = TRUE;
   }
-  if ($offline) {
-    $suggestions[] = 'maintenance_page__offline';
+  $suggestions = [];
+  if (isset($offline) || defined('MAINTENANCE_MODE')) {
+    $suggestions[] = 'page__maintenance__offline';
   }
 
   return $suggestions;
 }
 
 /**
+ * Prepares variables for maintenance page templates.
+ *
+ * Default template: page--maintenance.html.twig.
+ *
+ * @param array $variables
+ *   An associative array containing:
+ *   - content - An array of page content.
+ *
+ * @see system_page_attachments()
+ */
+function system_preprocess_page__maintenance(&$variables) {
+  // @see system_page_attachments()
+  $variables['#attached']['library'][] = 'system/maintenance';
+
+  // Maintenance page and install page need branding info in variables because
+  // there is no blocks.
+  $site_config = \Drupal::config('system.site');
+  $variables['logo'] = theme_get_setting('logo.url');
+  $variables['site_name'] = $site_config->get('name');
+  $variables['site_slogan'] = $site_config->get('slogan');
+}
+
+/**
+ * Prepares variables for install page templates.
+ *
+ * Default template: page--maintenance--install.html.twig.
+ *
+ * @param array $variables
+ *   An associative array containing:
+ *   - content - An array of page content.
+ *
+ * @see template_preprocess_page__maintenance()
+ */
+function system_preprocess_page__maintenance__install(&$variables) {
+  // Override the site name that is displayed on the page, since Drupal is
+  // still in the process of being installed.
+  $distribution_name = drupal_install_profile_distribution_name();
+  $variables['site_name'] = $distribution_name;
+}
+
+/**
  * Implements hook_theme_suggestions_HOOK().
  */
 function system_theme_suggestions_region(array $variables) {
@@ -511,11 +543,11 @@ function system_filetransfer_info() {
 /**
  * Implements hook_page_attachments().
  *
- * @see template_preprocess_maintenance_page()
+ * @see system_preprocess_page__maintenance()
  * @see \Drupal\Core\EventSubscriber\ActiveLinkResponseFilter
  */
 function system_page_attachments(array &$page) {
-  // Ensure the same CSS is loaded in template_preprocess_maintenance_page().
+  // Ensure the same CSS is loaded in system_preprocess_page__maintenance().
   $page['#attached']['library'][] = 'system/base';
   if (\Drupal::service('router.admin_context')->isAdminRoute()) {
     $page['#attached']['library'][] = 'system/admin';
diff --git a/core/themes/bartik/css/maintenance-page.css b/core/themes/bartik/css/maintenance-page.css
index dd473d4..f8cc373 100644
--- a/core/themes/bartik/css/maintenance-page.css
+++ b/core/themes/bartik/css/maintenance-page.css
@@ -1,8 +1,8 @@
-body.maintenance-page {
+body.page--maintenance {
   background-color: #fff;
   color: #000;
 }
-.maintenance-page #page-wrapper {
+.page--maintenance #page-wrapper {
   background: #fff;
   margin-left: auto;
   margin-right: auto;
@@ -11,71 +11,71 @@ body.maintenance-page {
   border: 1px solid #ddd;
   margin-top: 40px;
 }
-.maintenance-page #page {
+.page--maintenance #page {
   margin: 10px;
 }
-.maintenance-page #main-wrapper {
+.page--maintenance #main-wrapper {
   min-height: inherit;
 }
-.maintenance-page #header,
-.maintenance-page #messages {
+.page--maintenance #header,
+.page--maintenance #messages {
   width: auto;
 }
-.maintenance-page #main {
+.page--maintenance #main {
   margin: 0;
 }
-.maintenance-page .content .section {
+.page--maintenance .content .section {
   padding: 0 0 0 10px; /* LTR */
 }
-[dir="rtl"] .maintenance-page .content .section {
+[dir="rtl"] .page--maintenance .content .section {
   padding-left: 0;
   padding-right: 10px;
 }
-.maintenance-page #header {
+.page--maintenance #header {
   background-color: #fff;
   background-image: none;
 }
-.maintenance-page .site-branding-text {
+.page--maintenance .site-branding-text {
   margin-bottom: 50px;
   margin-left: 0; /* LTR */
   padding-top: 20px;
   font-size: 90%;
 }
-[dir="rtl"] .maintenance-page .site-branding-text {
+[dir="rtl"] .page--maintenance .site-branding-text {
   margin-right: 0;
 }
-.maintenance-page .site-branding-text,
-.maintenance-page .site-branding-text a,
-.maintenance-page .site-branding-text a:hover,
-.maintenance-page .site-branding-text a:focus {
+.page--maintenance .site-branding-text,
+.page--maintenance .site-branding-text a,
+.page--maintenance .site-branding-text a:hover,
+.page--maintenance .site-branding-text a:focus {
   color: #777;
 }
-.maintenance-page  .page-title {
+.page--maintenance  .page-title {
   line-height: 1em;
   margin-top: 0;
 }
-.maintenance-page #messages {
+.page--maintenance #messages {
   padding: 0;
   margin-top: 30px;
 }
-.maintenance-page #messages div.messages {
+.page--maintenance #messages div.messages {
   margin: 0;
 }
 @media all and (min-width: 800px) {
-  .maintenance-page #page-wrapper {
+  .page--maintenance #page-wrapper {
     width: 800px;
   }
-  .maintenance-page #header div.section,
-  .maintenance-page #main {
+  .page--maintenance #header div.section,
+  .page--maintenance #main {
     width: 700px;
   }
-  .maintenance-page #messages div.section {
+  .page--maintenance #messages div.section {
     padding: 0;
     width: auto;
   }
 }
 @media all and (min-width: 600px) { /* @TODO find the proper breakpoint */
-  .maintenance-page #page {
+  .page--maintenance #page {
     margin: 20px 40px 40px;
   }
 }
diff --git a/core/themes/seven/css/theme/install-page.css b/core/themes/seven/css/theme/install-page.css
index 3a2f217..4558c2f 100644
--- a/core/themes/seven/css/theme/install-page.css
+++ b/core/themes/seven/css/theme/install-page.css
@@ -3,9 +3,9 @@
  * Installation styling.
  *
  * Unfortunately we have to make our styling quite strong, to override the
- * .maintenance-page styling.
+ * .page--maintenance styling.
  */
-.install-page {
+.page--maintenance--install {
   background-color: #1275b2;
   background-image:
     url(../../images/noise-low.png),
@@ -17,28 +17,28 @@
   background-position: left top, 50% 50%; /* LTR */
   min-height: 100%;
 }
-[dir="rtl"] .install-page {
+[dir="rtl"] .page--maintenance--install {
   background-position: right top, 50% 50%;
 }
 
 /**
  * Password widget
  */
-.install-page .password-parent,
-.install-page .confirm-parent {
+.page--maintenance--install .password-parent,
+.page--maintenance--install .confirm-parent {
   width: auto;
 }
-.install-page .form-item .password-suggestions {
+.page--maintenance--install .form-item .password-suggestions {
   float: none;
   width: auto;
 }
-.install-page table td {
+.page--maintenance--install table td {
   word-break: break-word;
 }
 
 @media all and (max-width: 1010px) and (min-width: 48em) {
-  .install-page .password-strength,
-  .install-page .confirm-parent {
+  .page--maintenance--install .password-strength,
+  .page--maintenance--install .confirm-parent {
     width: 100%;
   }
   .install-configure-form .form-type-password {
diff --git a/core/themes/seven/css/theme/maintenance-page.css b/core/themes/seven/css/theme/maintenance-page.css
index 6784343..2a37575 100644
--- a/core/themes/seven/css/theme/maintenance-page.css
+++ b/core/themes/seven/css/theme/maintenance-page.css
@@ -2,7 +2,7 @@
  * @file
  * Maintenance theming.
  */
-.maintenance-page {
+.page--maintenance {
   background-color: #e0e0d8;
   background-image: -webkit-radial-gradient(hsl(203, 2%, 90%), hsl(203, 2%, 95%));
   background-image: radial-gradient(hsl(203, 2%, 90%), hsl(203, 2%, 95%));
@@ -10,7 +10,7 @@
   background-position: left top, 50% 50%; /* LTR */
   min-height: 100%;
 }
-[dir="rtl"] .maintenance-page {
+[dir="rtl"] .page--maintenance {
   background-position: right top, 50% 50%;
 }
 
@@ -129,13 +129,13 @@
   html {
     display: table;
   }
-  .install-page,
-  .maintenance-page {
+  .page--maintenance--install,
+  .page--maintenance {
     display: table-cell;
     padding: 1em 0;
     vertical-align: middle;
   }
-  html, .install-page, .maintenance-page {
+  html, .page--maintenance--install, .page--maintenance {
     margin: 0;
     width: 100%;
     height: 100%;