diff -u b/core/lib/Drupal/Core/Form/FormBuilder.php b/core/lib/Drupal/Core/Form/FormBuilder.php
--- b/core/lib/Drupal/Core/Form/FormBuilder.php
+++ b/core/lib/Drupal/Core/Form/FormBuilder.php
@@ -390,7 +390,7 @@
    * {@inheritdoc}
    */
   public function setCache($form_build_id, $form, $form_state) {
-    $expire = \Drupal::config('system.performance')->get('cache.expire.form');
+    $expire = \Drupal::config('system.performance')->get('cache.form.expire');
     // Cache form structure.
     if (isset($form)) {
       if ($this->currentUser()->isAuthenticated()) {
diff -u b/core/modules/system/config/schema/system.schema.yml b/core/modules/system/config/schema/system.schema.yml
--- b/core/modules/system/config/schema/system.schema.yml
+++ b/core/modules/system/config/schema/system.schema.yml
@@ -195,11 +195,11 @@
             max_age:
               type: integer
               label: 'Max age of page cache'
-        expire:
+        form:
           type: mapping
-          label: 'Cache lifetime timeouts'
+          label: 'Form cache settings'
           mapping:
-            form:
+            expire:
               type: integer
               label: 'Form cache timeout'
     css:
diff -u b/core/modules/system/config/system.performance.yml b/core/modules/system/config/system.performance.yml
--- b/core/modules/system/config/system.performance.yml
+++ b/core/modules/system/config/system.performance.yml
@@ -2,8 +2,8 @@
   page:
     use_internal: false
     max_age: 0
-  expire:
-    form: 21600
+  form:
+    expire: 21600
 css:
   preprocess: false
   gzip: true
only in patch2:
unchanged:
--- a/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php
+++ b/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php
@@ -41,6 +41,7 @@ public function setUp() {
 
     $container = new ContainerBuilder();
     $container->set('url_generator', $this->urlGenerator);
+    $container->set('config.factory', $this->getConfigFactoryStub(array()));
     \Drupal::setContainer($container);
   }