diff --git a/modules/contrib/block_class/block_class.module b/modules/contrib/block_class/block_class.module
index eec5ba5..86bf656 100644
--- a/modules/contrib/block_class/block_class.module
+++ b/modules/contrib/block_class/block_class.module
@@ -5,8 +5,7 @@
  */
 
 use Drupal\custom_block\Entity\CustomBlock;
-
-
+use Drupal\Core\Form\FormStateInterface;
 /**
  * Implements hook_permission().
  */
@@ -19,10 +18,10 @@ function block_class_permission() {
 }
 
 /**
- * Implementation of hook_form_alter()
+ * Implements hook_form_FORM_ID_alter().
  */
-function block_class_form_alter(&$form, &$form_state, $form_id) {
-  if (user_access('administer block classes') && $form_id == 'block_form') {
+function block_class_form_block_form_alter(&$form, FormStateInterface $form_state, $form_id) {
+  if (\Drupal::currentUser()->hasPermission('administer block classes')) {
     $config = \Drupal::config('block_class.settings');
     $block_id = $form['id']['#default_value'];
 
@@ -41,18 +40,18 @@ function block_class_form_alter(&$form, &$form_state, $form_id) {
 /**
  * Form submission callback.
  */
-function block_class_form_submit($form, &$form_state) {
-  $config = \Drupal::config('block_class.settings');
-  $block_id = $form_state['values']['id'];
+function block_class_form_submit($form, FormStateInterface &$form_state) {
+  $config = \Drupal::service('config.factory')->getEditable('block_class.settings');
 
-  $classes = trim($form_state['values']['block_classes']);
+  $block_id = $form_state->getValue('id');
+  $classes = trim($form_state->getValue('block_classes'));
 
   if(empty($classes)) {
-    $config->clear($block_id.'.block_classes',$classes);
+    $config->clear($block_id . '.block_classes', $classes);
     $config->save();
   }
   else {
-    $config->set($block_id.'.block_classes',$classes);
+    $config->set($block_id . '.block_classes', $classes);
     $config->save();
   }
 }
@@ -61,8 +60,14 @@ function block_class_form_submit($form, &$form_state) {
  * Implements hook_preprocess_hook().
  */
 function block_class_preprocess_block(&$vars) {
-  $config = \Drupal::config('block_class.settings');
-  $block_id = $vars['elements']['#block']->id;
-  $classes = $config->get($block_id.'.block_classes');
-  $vars['attributes']['class'][] = $classes;
+  $config = \Drupal::service('config.factory')->getEditable('block_class.settings');
+
+  $block_id = $vars['elements']['#id'];
+
+  if ($block_id) {
+    $classes = $config->get($block_id . '.block_classes');
+    if ($classes) {
+      $vars['attributes']['class'][] = $classes;
+    }
+  }
 }