diff --git a/core/modules/block/lib/Drupal/block/BlockFormController.php b/core/modules/block/lib/Drupal/block/BlockFormController.php
index 7b55d62..c7fb3cd 100644
--- a/core/modules/block/lib/Drupal/block/BlockFormController.php
+++ b/core/modules/block/lib/Drupal/block/BlockFormController.php
@@ -251,7 +251,7 @@ public function form(array $form, array &$form_state) {
         '#ajax' => array(
           'callback' => array($this, 'themeSwitch'),
           'wrapper' => 'edit-block-region-wrapper',
-         ),
+        ),
       );
     }
     // Region settings.
@@ -293,7 +293,7 @@ public function validate(array $form, array &$form_state) {
 
     $entity = $this->entity;
     if ($entity->isNew()) {
-      form_set_value($form['id'], $entity->get('theme') . '.' . $form_state['values']['machine_name'], $form_state);
+      form_set_value($form['id'], $form_state['values']['theme'] . '.' . $form_state['values']['machine_name'], $form_state);
     }
     if (!empty($form['machine_name']['#disabled'])) {
       $config_id = explode('.', $form_state['values']['machine_name']);
@@ -329,7 +329,7 @@ public function submit(array $form, array &$form_state) {
 
     drupal_set_message($this->t('The block configuration has been saved.'));
     Cache::invalidateTags(array('content' => TRUE));
-    $form_state['redirect'] = array('admin/structure/block/list/' . $entity->get('theme'), array(
+    $form_state['redirect'] = array('admin/structure/block/list/' . $form_state['values']['theme'], array(
       'query' => array('block-placement' => drupal_html_class($this->entity->id())),
     ));
   }
diff --git a/core/modules/block/lib/Drupal/block/Tests/BlockTest.php b/core/modules/block/lib/Drupal/block/Tests/BlockTest.php
index 018a2b8..13064c6 100644
--- a/core/modules/block/lib/Drupal/block/Tests/BlockTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockTest.php
@@ -156,6 +156,8 @@ public function testBlockThemeSelector() {
 
     $this->drupalPost('admin/structure/block/add/system_powered_by_block', $block, t('Save block'));
     $this->assertText(t('The block configuration has been saved.'));
+    $elements = $this->xpath('//div[@id = :id]', array(':id' => drupal_html_id('block-' . $block['machine_name'])));
+    $this->assertTrue(!empty($elements), 'The block was found.');
   }
 
   /**