diff --git a/core/modules/block/src/Tests/BlockViewBuilderTest.php b/core/modules/block/src/Tests/BlockViewBuilderTest.php
index bd2a986..11ef6b4 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();
diff --git a/core/modules/block/templates/block-list.html.twig b/core/modules/block/templates/block-list.html.twig
deleted file mode 100644
index 854d3ce..0000000
--- a/core/modules/block/templates/block-list.html.twig
+++ /dev/null
@@ -1,23 +0,0 @@
-{#
-/**
- * @file
- * Two column template for the block add/edit form.
- *
- * This template will be used when a block edit form specifies 'block_edit_form'
- * as its #theme callback.  Otherwise, by default, block add/edit forms will be
- * themed by form.html.twig.
- *
- * Available variables:
- * - form: The block add/edit form.
- *
- * @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>
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/themes/classy/templates/block-list.html.twig b/core/themes/classy/templates/block-list.html.twig
new file mode 100644
index 0000000..7550689
--- /dev/null
+++ b/core/themes/classy/templates/block-list.html.twig
@@ -0,0 +1,17 @@
+{#
+/**
+ * @file
+ * Two column template for the block add/edit form.
+ *
+ * This template will be used when a block edit form specifies 'block_edit_form'
+ * as its #theme callback.  Otherwise, by default, block add/edit forms will be
+ * themed by form.html.twig.
+ *
+ * Available variables:
+ * - form: The block add/edit form.
+ *
+ * @ingroup themeable
+ */
+#}
+<div>
+  {{ form }}