diff --git a/core/modules/forum/forum.admin.inc b/core/modules/forum/forum.admin.inc
index 2a8a50d..66a20b2 100644
--- a/core/modules/forum/forum.admin.inc
+++ b/core/modules/forum/forum.admin.inc
@@ -124,22 +124,6 @@ function forum_form_submit($form, &$form_state) {
 }
 
 /**
- * Returns HTML for a forum form.
- *
- * By default this does not alter the appearance of a form at all, but is
- * provided as a convenience for themers.
- *
- * @param $variables
- *   An associative array containing:
- *   - form: A render element representing the form.
- *
- * @ingroup themeable
- */
-function theme_forum_form($variables) {
-  return drupal_render_children($variables['form']);
-}
-
-/**
  * Form constructor for adding and editing forum containers.
  *
  * @param \Drupal\taxonomy\Plugin\Core\Entity\Term $term
diff --git a/core/modules/forum/forum.module b/core/modules/forum/forum.module
index 42d7326..c23b02f 100644
--- a/core/modules/forum/forum.module
+++ b/core/modules/forum/forum.module
@@ -83,6 +83,7 @@ function forum_theme() {
     'forum_form' => array(
       'render element' => 'form',
       'file' => 'forum.admin.inc',
+      'template' => 'forum-form',
     ),
   );
 }
diff --git a/core/modules/forum/templates/forum-form.html.twig b/core/modules/forum/templates/forum-form.html.twig
new file mode 100644
index 0000000..e3a76ec
--- /dev/null
+++ b/core/modules/forum/templates/forum-form.html.twig
@@ -0,0 +1,15 @@
+{#
+/**
+ * @see
+ * Default theme implementation for a forum form.
+ *
+ * Available variables:
+ * - form: The complete form. Use 'form' to print the entire form, or print a
+ *   subset such as 'form.title'.
+ *
+ * @see template_preprocess()
+ *
+ * @ingroup themeable
+ */
+#}
+{{ form }}