diff --git a/core/modules/block/src/Tests/BlockViewBuilderTest.php b/core/modules/block/src/Tests/BlockViewBuilderTest.php
index 2ddbcab..b25998e 100644
--- a/core/modules/block/src/Tests/BlockViewBuilderTest.php
+++ b/core/modules/block/src/Tests/BlockViewBuilderTest.php
@@ -58,7 +58,7 @@ protected function setUp() {
     // Create a block with only required values.
     $this->block = $this->controller->create(array(
       'id' => 'test_block',
-      'theme' => 'stark',
+      'theme' => 'classy',
       'plugin' => 'test_cache',
     ));
     $this->block->save();
@@ -74,7 +74,7 @@ public function testBasicRendering() {
 
     $entity = $this->controller->create(array(
       'id' => 'test_block1',
-      'theme' => 'stark',
+      'theme' => 'classy',
       'plugin' => 'test_html',
     ));
     $entity->save();
@@ -98,7 +98,7 @@ public function testBasicRendering() {
     // Test the rendering of a block with a given title.
     $entity = $this->controller->create(array(
       'id' => 'test_block2',
-      'theme' => 'stark',
+      'theme' => 'classy',
       'plugin' => 'test_html',
       'settings' => array(
         'label' => 'Powered by Bananas',
@@ -128,7 +128,7 @@ public function testBlockViewBuilderCache() {
     // Create an empty block.
     $this->block = $this->controller->create(array(
       'id' => 'test_block',
-      'theme' => 'stark',
+      'theme' => 'classy',
       'plugin' => 'test_cache',
     ));
     $this->block->save();
@@ -215,7 +215,7 @@ public function testBlockViewBuilderAlter() {
     $request->setMethod('GET');
 
     $default_keys = array('entity_view', 'block', 'test_block', 'en', 'cache_context.theme');
-    $default_tags = array('block_view', 'block:test_block', 'theme:stark', 'block_plugin:test_cache');
+    $default_tags = array('block_view', 'block:test_block', 'theme:classy', 'block_plugin:test_cache');
 
     // Advanced: cached block, but an alter hook adds an additional cache key.
     $this->setBlockCacheConfig(array(
@@ -230,7 +230,7 @@ public function testBlockViewBuilderAlter() {
     $this->assertIdentical(drupal_render($build), '');
     $cache_entry = $this->container->get('cache.render')->get($cid);
     $this->assertTrue($cache_entry, 'The block render element has been cached with the expected cache ID.');
-    $expected_tags = array('block_view', 'block:test_block', 'theme:stark', 'block_plugin:test_cache', 'rendered');
+    $expected_tags = array('block_view', 'block:test_block', 'theme:classy', 'block_plugin:test_cache', 'rendered');
     sort($expected_tags);
     $this->assertIdentical($cache_entry->tags, $expected_tags, 'The block render element has been cached with the expected cache tags.');
     $this->container->get('cache.render')->delete($cid);
@@ -246,7 +246,7 @@ public function testBlockViewBuilderAlter() {
     $this->assertIdentical(drupal_render($build), '');
     $cache_entry = $this->container->get('cache.render')->get($cid);
     $this->assertTrue($cache_entry, 'The block render element has been cached with the expected cache ID.');
-    $expected_tags = array('block_view', 'block:test_block', 'theme:stark', 'block_plugin:test_cache', $alter_add_tag, 'rendered');
+    $expected_tags = array('block_view', 'block:test_block', 'theme:classy', 'block_plugin:test_cache', $alter_add_tag, 'rendered');
     sort($expected_tags);
     $this->assertIdentical($cache_entry->tags, $expected_tags, 'The block render element has been cached with the expected cache tags.');
     $this->container->get('cache.render')->delete($cid);
diff --git a/core/modules/block/templates/block-list.html.twig b/core/modules/block/templates/block-list.html.twig
index 854d3ce..29c3647 100644
--- a/core/modules/block/templates/block-list.html.twig
+++ b/core/modules/block/templates/block-list.html.twig
@@ -13,11 +13,6 @@
  * @ingroup themeable
  */
 #}
-<div class="layout-block-list clearfix">
-  <div class="layout-region block-list-primary">
-    {{ form|without('place_blocks') }}
-  </div>
-  <div class="layout-region block-list-secondary">
-    {{ form.place_blocks }}
-  </div>
+<div>
+  {{ form }}
 </div>
diff --git a/core/modules/block/templates/block.html.twig b/core/modules/block/templates/block.html.twig
index aa750cb..b7a3ff7 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>
   {{ title_prefix }}
   {% if label %}
     <h2{{ title_attributes }}>{{ label }}</h2>
diff --git a/core/modules/block_content/templates/block-content-add-list.html.twig b/core/modules/block_content/templates/block-content-add-list.html.twig
index e5a5d97..0810461 100644
--- a/core/modules/block_content/templates/block-content-add-list.html.twig
+++ b/core/modules/block_content/templates/block-content-add-list.html.twig
@@ -15,7 +15,7 @@
  */
 #}
 {% spaceless %}
-  <dl class="node-type-list">
+  <dl>
     {% for type in types %}
       <dt>{{ type.link }}</dt>
       <dd>{{ type.description }}</dd>
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