diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index b577124..deab439 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -513,7 +513,6 @@ function template_preprocess_block(&$variables) {
   $variables['content'] = $variables['elements']['content'];
 
   $variables['attributes']['class'][] = 'block';
-  $variables['attributes']['class'][] = drupal_html_class($variables['configuration']['module']);
   $variables['attributes']['class'][] = drupal_html_class($variables['plugin_id']);
   $variables['attributes']['id'] = drupal_html_id('block-' . $variables['elements']['#block']->id());
 
diff --git a/core/modules/block/lib/Drupal/block/Tests/Views/DisplayBlockTest.php b/core/modules/block/lib/Drupal/block/Tests/Views/DisplayBlockTest.php
index 4a1e64d..90b6042 100644
--- a/core/modules/block/lib/Drupal/block/Tests/Views/DisplayBlockTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/Views/DisplayBlockTest.php
@@ -67,7 +67,7 @@ public function testBlockCategory() {
     // base table.
     $arguments = array(
       ':id' => 'edit-category-lists-views',
-      ':li_class' => 'views-block' . drupal_html_class($edit['id']) . '-block-1',
+      ':li_class' => 'views-block--' . drupal_html_class($edit['id']) . '-block-1',
       ':href' => url('admin/structure/block/add/views_block:' . $edit['id'] . '-block_1/stark'),
       ':text' => $edit['label'],
     );
@@ -103,7 +103,7 @@ public function testBlockCategory() {
 
     $arguments = array(
       ':id' => 'edit-category-lists-views',
-      ':li_class' => 'views-block' . drupal_html_class($edit['id']) . '-block-2',
+      ':li_class' => 'views-block--' . drupal_html_class($edit['id']) . '-block-2',
       ':href' => url('admin/structure/block/add/views_block:' . $edit['id'] . '-block_2/stark'),
       ':text' => $edit['label'],
     );
@@ -112,7 +112,7 @@ public function testBlockCategory() {
 
     $arguments = array(
       ':id' => $category_id,
-      ':li_class' => 'views-block' . drupal_html_class($edit['id']) . '-block-3',
+      ':li_class' => 'views-block--' . drupal_html_class($edit['id']) . '-block-3',
       ':href' => url('admin/structure/block/add/views_block:' . $edit['id'] . '-block_3/stark'),
       ':text' => $edit['label'],
     );