diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index c8b88f2..0a74451 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1784,14 +1784,14 @@ function theme_mark($variables) {
 function template_preprocess_item_list(&$variables) {
   $variables['title'] = (string) $variables['title'];
 
-  // Prepare for adding classes to each item.
-  $num_items = count($variables['items']);
-  $i = 0;
   foreach ($variables['items'] as &$item) {
-    $i++;
     $attributes = array();
     // If the item value is an array, then it is a render array.
     if (is_array($item)) {
+      // List items support attributes via the 'attributes' property.
+      if (isset($item['attributes']) && is_array($item['attributes'])) {
+        $attributes = $item['attributes'];
+      }
       // Determine whether there are any child elements in the item that are not
       // fully-specified render arrays. If there are any, then the child
       // elements present nested lists and we automatically inherit the render
@@ -1823,9 +1823,11 @@ function template_preprocess_item_list(&$variables) {
     }
     else {
       // Turn the item into an array if it wasn't one already.
-      $item = array('#markup' => $item);
+      $item = array('value' => $item);
     }
 
+    // Store item attributes for Twig.
+    $item['attributes'] = new Attribute($attributes);
   }
 }
 
diff --git a/core/modules/system/templates/item-list.html.twig b/core/modules/system/templates/item-list.html.twig
index 3315c0b..2936224 100644
--- a/core/modules/system/templates/item-list.html.twig
+++ b/core/modules/system/templates/item-list.html.twig
@@ -30,7 +30,7 @@
       <ol{{ attributes }}>
     {%- endif %}
       {%- for item in items -%}
-        <li>{{ item }}</li>
+        <li {{ item.attributes }}>{{ item.value }}</li>
       {%- endfor -%}
     {%- if list_type == 'ul' -%}
       </ul>