diff --git a/core/lib/Drupal/Core/Condition/ConditionPluginBase.php b/core/lib/Drupal/Core/Condition/ConditionPluginBase.php
index 41c7c70..68e0f35 100644
--- a/core/lib/Drupal/Core/Condition/ConditionPluginBase.php
+++ b/core/lib/Drupal/Core/Condition/ConditionPluginBase.php
@@ -41,8 +41,9 @@ public function isNegated() {
    * {@inheritdoc}
    */
   public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
-    // @todo Do not abuse context mappings to hold context objects.
-    $contexts = $form_state->get('gathered_contexts') ?: [];
+    $temporary = $form_state->getTemporary();
+    $contexts = isset($temporary['gathered_contexts']) ? $temporary['gathered_contexts'] : [];
+
     $form['context_mapping'] = $this->addContextAssignmentElement($contexts);
     $form['context_mapping']['#weight'] = -100;
     $form['negate'] = array(
diff --git a/core/modules/block/src/BlockForm.php b/core/modules/block/src/BlockForm.php
index c0cf9d6..2755b39 100644
--- a/core/modules/block/src/BlockForm.php
+++ b/core/modules/block/src/BlockForm.php
@@ -103,7 +103,9 @@ public function form(array $form, FormStateInterface $form_state) {
 
     // Store the gathered contexts in the form state for other objects to use
     // during form building.
-    $form_state->set('gathered_contexts', $this->dispatcher->dispatch(BlockEvents::ADMINISTRATIVE_CONTEXT, new BlockContextEvent())->getContexts());
+    $temporary = $form_state->getTemporary();
+    $temporary['gathered_contexts'] = $this->dispatcher->dispatch(BlockEvents::ADMINISTRATIVE_CONTEXT, new BlockContextEvent())->getContexts();
+    $form_state->setTemporary($temporary);
 
     $form['#tree'] = TRUE;
     $form['settings'] = $entity->getPlugin()->buildConfigurationForm(array(), $form_state);
@@ -165,8 +167,6 @@ public function form(array $form, FormStateInterface $form_state) {
       drupal_get_path('module', 'block') . '/css/block.admin.css',
     );
 
-    // Clear out the gathered contexts.
-    $form_state->set('gathered_contexts', []);
     return $form;
   }
 
diff --git a/core/modules/system/tests/modules/condition_test/src/FormController.php b/core/modules/system/tests/modules/condition_test/src/FormController.php
index e81127d..1f13755 100644
--- a/core/modules/system/tests/modules/condition_test/src/FormController.php
+++ b/core/modules/system/tests/modules/condition_test/src/FormController.php
@@ -42,9 +42,6 @@ public function __construct() {
    * {@inheritdoc}
    */
   public function buildForm(array $form, FormStateInterface $form_state) {
-    // Clear out the gathered contexts.
-    $form_state->set('gathered_contexts', []);
-
     $form = $this->condition->buildConfigurationForm($form, $form_state);
     $form['actions']['submit'] = array(
       '#type' => 'submit',