diff --git c/core/modules/forum/lib/Drupal/forum/Form/Overview.php w/core/modules/forum/lib/Drupal/forum/Form/Overview.php
index 94a178a..47b2140 100644
--- c/core/modules/forum/lib/Drupal/forum/Form/Overview.php
+++ w/core/modules/forum/lib/Drupal/forum/Form/Overview.php
@@ -60,7 +60,7 @@ public function getFormID() {
    * {@inheritdoc}
    */
   public function buildForm(array $form, array &$form_state) {
-    $forum_config = $this->configFactory->get('forum.settings');
+    $forum_config = $this->config('forum.settings');
     $vid = $forum_config->get('vocabulary');
     $vocabulary = $this->entityManager->getStorageController('taxonomy_vocabulary')->load($vid);
     if (!$vocabulary) {