diff --git a/core/includes/theme.maintenance.inc b/core/includes/theme.maintenance.inc
index 2ceec4a..e880d00 100644
--- a/core/includes/theme.maintenance.inc
+++ b/core/includes/theme.maintenance.inc
@@ -7,6 +7,7 @@
 
 use Drupal\Component\Utility\Unicode;
 use Drupal\Core\Site\Settings;
+use Drupal\Core\Template\Attribute;
 
 /**
  * Sets up the theming system for maintenance page.
@@ -104,43 +105,39 @@ function _drupal_maintenance_theme() {
 }
 
 /**
- * Returns HTML for a list of maintenance tasks to perform.
+ * Prepares variables for maintenance task list templates.
  *
- * @param $variables
+ * Default template: task-list.html.twig.
+ *
+ * @param array $variables
  *   An associative array containing:
  *   - items: An associative array of maintenance tasks.
  *     It's the caller's responsibility to ensure this array's items contain no
  *     dangerous HTML such as SCRIPT tags.
  *   - active: The key for the currently active maintenance task.
  *
- * @ingroup themeable
  */
-function theme_task_list($variables) {
+function template_preprocess_task_list(&$variables) {
   $items = $variables['items'];
   $active = $variables['active'];
 
   $done = isset($items[$active]) || $active == NULL;
-  $output = '<h2 class="visually-hidden">Installation tasks</h2>';
-  $output .= '<ol class="task-list">';
+  $tasks = array();
 
   foreach ($items as $k => $item) {
+    $tasks[$k]['item'] = $item;
+    $tasks[$k]['attributes'] = new Attribute(array('class' => array()));
     if ($active == $k) {
-      $class = 'active';
-      $status = '(' . t('active') . ')';
+      $tasks[$k]['attributes']['class'][] = 'active';
+      $tasks[$k]['status'] = t('active');
       $done = FALSE;
     }
     else {
-      $class = $done ? 'done' : '';
-      $status = $done ? '(' . t('done') . ')' : '';
+      $tasks[$k]['attributes']['class'][] = $done ? 'done' : '';
+      $tasks[$k]['status'] = $done ? t('done') : '';
     }
-    $output .= '<li';
-    $output .= ($class ? ' class="' . $class . '"' : '') . '>';
-    $output .= $item;
-    $output .= ($status ? '<span class="visually-hidden"> ' . $status . '</span>' : '');
-    $output .= '</li>';
   }
-  $output .= '</ol>';
-  return $output;
+  $variables['tasks'] = $tasks;
 }
 
 /**
diff --git a/core/modules/system/templates/task-list.html.twig b/core/modules/system/templates/task-list.html.twig
new file mode 100644
index 0000000..b707a0f
--- /dev/null
+++ b/core/modules/system/templates/task-list.html.twig
@@ -0,0 +1,25 @@
+{#
+/**
+ * @file
+ * Default theme implementation for a list of maintenance tasks to perform.
+ *
+ * Available variables:
+ * - tasks: A list of maintenance tasks to perform. Each item in the list has
+ *   the following variables:
+ *   - item: The maintenance task.
+ *   - attributes: HTML attributes for the maintenance task.
+ *   - status: (optional) Text describing the status of the maintenance task,
+ *     'active' or 'done'.
+ *
+ * @ingroup themeable
+ */
+#}
+<h2 class="visually-hidden">Installation tasks</h2>
+<ol class="task-list">
+{% for task in tasks %}
+  <li{{ task.attributes }}>
+    {{ task.item }}
+    {% if task.status %} <span class="visually-hidden">({{ task.status }})</span>{% endif %}
+  </li>
+{% endfor %}
+</ol>