diff --git a/core/modules/block/src/Tests/BlockViewBuilderTest.php b/core/modules/block/src/Tests/BlockViewBuilderTest.php
index bd2a986..d148ddd 100644
--- a/core/modules/block/src/Tests/BlockViewBuilderTest.php
+++ b/core/modules/block/src/Tests/BlockViewBuilderTest.php
@@ -83,7 +83,7 @@ public function testBasicRendering() {
     $entity = Block::load('test_block1');
     $output = entity_view($entity, 'block');
     $expected = array();
-    $expected[] = '<div id="block-test-block1" class="block block-block-test">';
+    $expected[] = '<div>';
     $expected[] = '  ';
     $expected[] = '    ';
     $expected[] = '      ';
@@ -107,7 +107,7 @@ public function testBasicRendering() {
     $entity->save();
     $output = entity_view($entity, 'block');
     $expected = array();
-    $expected[] = '<div id="block-test-block2" class="block block-block-test">';
+    $expected[] = '<div>';
     $expected[] = '  ';
     $expected[] = '      <h2>Powered by Bananas</h2>';
     $expected[] = '    ';
diff --git a/core/modules/block/templates/block-list.html.twig b/core/modules/block/templates/block-list.html.twig
index 854d3ce..bd3c6f7 100644
--- a/core/modules/block/templates/block-list.html.twig
+++ b/core/modules/block/templates/block-list.html.twig
@@ -13,11 +13,11 @@
  * @ingroup themeable
  */
 #}
-<div class="layout-block-list clearfix">
-  <div class="layout-region block-list-primary">
+<div>
+  <div>
     {{ form|without('place_blocks') }}
   </div>
-  <div class="layout-region block-list-secondary">
+  <div>
     {{ form.place_blocks }}
   </div>
 </div>
diff --git a/core/modules/block/templates/block.html.twig b/core/modules/block/templates/block.html.twig
index aa750cb..236b3cf 100644
--- a/core/modules/block/templates/block.html.twig
+++ b/core/modules/block/templates/block.html.twig
@@ -34,13 +34,7 @@
  * @ingroup themeable
  */
 #}
-{%
-  set classes = [
-    'block',
-    'block-' ~ configuration.provider|clean_class,
-  ]
-%}
-<div{{ attributes.addClass(classes) }}>
+<div{{ attributes }}>
   {{ title_prefix }}
   {% if label %}
     <h2{{ title_attributes }}>{{ label }}</h2>
diff --git a/core/modules/block/templates/block-list.html.twig b/core/themes/classy/templates/block-list.html.twig
similarity index 100%
copy from core/modules/block/templates/block-list.html.twig
copy to core/themes/classy/templates/block-list.html.twig
diff --git a/core/modules/block/templates/block.html.twig b/core/themes/classy/templates/block.html.twig
similarity index 100%
copy from core/modules/block/templates/block.html.twig
copy to core/themes/classy/templates/block.html.twig