diff --git a/core/lib/Drupal/Core/Block/BlockBase.php b/core/lib/Drupal/Core/Block/BlockBase.php
index 66f6cb3..58f79a3 100644
--- a/core/lib/Drupal/Core/Block/BlockBase.php
+++ b/core/lib/Drupal/Core/Block/BlockBase.php
@@ -163,8 +163,6 @@ protected function blockAccess(AccountInterface $account) {
    */
   public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
     $definition = $this->getPluginDefinition();
-    $contexts = $form_state->getTemporaryValue('gathered_contexts') ?: [];
-    $form['context_mapping'] = $this->addContextAssignmentElement($this, $contexts);
     $form['provider'] = array(
       '#type' => 'value',
       '#value' => $definition['provider'],
@@ -233,6 +231,9 @@ public function buildConfigurationForm(array $form, FormStateInterface $form_sta
       $form['cache']['contexts']['#description'] .= ' ' . t('This block is <em>always</em> varied by the following contexts: %required-context-list.', array('%required-context-list' => $required_context_list));
     }
 
+    // Add context form elements.
+    $contexts = $form_state->getTemporaryValue('gathered_contexts') ?: [];
+    $form['context_mapping'] = $this->addContextAssignmentElement($this, $contexts);
     // Add plugin-specific settings for this block type.
     $form += $this->blockForm($form, $form_state);
     return $form;
diff --git a/core/modules/block/src/Tests/BlockInterfaceTest.php b/core/modules/block/src/Tests/BlockInterfaceTest.php
index cb17bf7..716f6db 100644
--- a/core/modules/block/src/Tests/BlockInterfaceTest.php
+++ b/core/modules/block/src/Tests/BlockInterfaceTest.php
@@ -67,7 +67,6 @@ public function testBlockInterface() {
     $contexts = \Drupal::service("cache_contexts")->getLabels();
     unset($contexts['cache_context.theme']);
     $expected_form = array(
-      'context_mapping' => array(),
       'provider' => array(
         '#type' => 'value',
         '#value' => 'block_test',
@@ -113,6 +112,7 @@ public function testBlockInterface() {
           ),
         ),
       ),
+      'context_mapping' => array(),
       'display_message' => array(
         '#type' => 'textfield',
         '#title' => t('Display message'),