diff --git a/core/lib/Drupal/Core/Condition/ConditionPluginBase.php b/core/lib/Drupal/Core/Condition/ConditionPluginBase.php
index 5aed43f..98d87dd 100644
--- a/core/lib/Drupal/Core/Condition/ConditionPluginBase.php
+++ b/core/lib/Drupal/Core/Condition/ConditionPluginBase.php
@@ -98,6 +98,8 @@ public function isNegated() {
    * {@inheritdoc}
    */
   public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
+    // Retrieve the globally available contexts.
+    $contexts = $this->getContextRepository()->getAvailableContexts();
     // Getting contexts from the form state is deprecated, as it means this
     // implementation of
     // \Drupal\Core\Plugin\PluginFormInterface::buildConfigurationForm() is not
@@ -105,13 +107,13 @@ public function buildConfigurationForm(array $form, FormStateInterface $form_sta
     // \Drupal\block\BlockForm.
     // @todo Remove this before Drupal 9.0.0.
     if ($form_state->hasTemporaryValue('gathered_contexts')) {
-      $contexts = $form_state->getTemporaryValue('gathered_contexts');
+      $contexts = array_merge($contexts, $form_state->getTemporaryValue('gathered_contexts'));
     }
-    else {
-      $contexts = $this->getContextRepository()->getAvailableContexts();
+    foreach ($contexts as $context_id => $context) {
+      $this->setContext($context_id, $context);
     }
 
-    $form['context_mapping'] = $this->addContextAssignmentElement($this, $contexts);
+    $form['context_mapping'] = $this->addContextAssignmentElement($this, $this->getContexts());
     $form['negate'] = array(
       '#type' => 'checkbox',
       '#title' => $this->t('Negate the condition'),
diff --git a/core/lib/Drupal/Core/Plugin/Context/ContextRepositoryInterface.php b/core/lib/Drupal/Core/Plugin/Context/ContextRepositoryInterface.php
index 6d7d609..a05fdaf 100644
--- a/core/lib/Drupal/Core/Plugin/Context/ContextRepositoryInterface.php
+++ b/core/lib/Drupal/Core/Plugin/Context/ContextRepositoryInterface.php
@@ -39,7 +39,7 @@ public function getRuntimeContexts(array $context_ids);
    * Gets all available contexts for the purposes of configuration.
    *
    * @return \Drupal\Core\Plugin\Context\ContextInterface[]
-   *   All available contexts.
+   *   All available contexts, keyed by context ID.
    */
   public function getAvailableContexts();