diff --git a/core/modules/forum/src/Form/ContainerForm.php b/core/modules/forum/src/Form/ContainerForm.php
index d12d0982a340a8f627b41d7dd2cf42266ca944f7..0b011245743192d2bc99a61ff37a599cf8a6255a 100644
--- a/core/modules/forum/src/Form/ContainerForm.php
+++ b/core/modules/forum/src/Form/ContainerForm.php
@@ -20,9 +20,8 @@ class ContainerForm extends ForumForm {
    * {@inheritdoc}
    */
   public function form(array $form, FormStateInterface $form_state) {
-    $taxonomy_term = $this->entity;
     // Build the bulk of the form from the parent forum form.
-    $form = parent::form($form, $form_state, $taxonomy_term);
+    $form = parent::form($form, $form_state);
 
     // Set the title and description of the name field.
     $form['name']['#title'] = $this->t('Container name');
diff --git a/core/modules/forum/src/Form/ForumForm.php b/core/modules/forum/src/Form/ForumForm.php
index ed0a7683a5d389bfe21a96c38230f8c2388326f7..80c2d38ca98593ad880b89914d42da43149157b3 100644
--- a/core/modules/forum/src/Form/ForumForm.php
+++ b/core/modules/forum/src/Form/ForumForm.php
@@ -29,9 +29,8 @@ class ForumForm extends TermForm {
    * {@inheritdoc}
    */
   public function form(array $form, FormStateInterface $form_state) {
-    $taxonomy_term = $this->entity;
-    // Build the bulk of the form from the parent taxonomy term form.
-    $form = parent::form($form, $form_state, $taxonomy_term);
+    // Build the bulk of the form from the parent form.
+    $form = parent::form($form, $form_state);
 
     // Set the title and description of the name field.
     $form['name']['#title'] = $this->t('Forum name');
@@ -48,7 +47,7 @@ public function form(array $form, FormStateInterface $form_state) {
 
     // Our parent field is different to the taxonomy term.
     $form['parent']['#tree'] = TRUE;
-    $form['parent'][0] = $this->forumParentSelect($taxonomy_term->id(), $this->t('Parent'));
+    $form['parent'][0] = $this->forumParentSelect($this->entity->id(), $this->t('Parent'));
 
     $form['#theme_wrappers'] = ['form__forum'];
     $this->forumFormType = $this->t('forum');