diff --git a/core/lib/Drupal/Core/Form/FormBuilder.php b/core/lib/Drupal/Core/Form/FormBuilder.php
index 43d15a6..70c8415 100644
--- a/core/lib/Drupal/Core/Form/FormBuilder.php
+++ b/core/lib/Drupal/Core/Form/FormBuilder.php
@@ -390,9 +390,7 @@ public function getCache($form_build_id, &$form_state) {
    * {@inheritdoc}
    */
   public function setCache($form_build_id, $form, $form_state) {
-    // 6 hours cache life time for forms should be plenty.
-    $expire = 21600;
-
+    $expire = \Drupal::config('system.form')->get('cache_expire');
     // Cache form structure.
     if (isset($form)) {
       if ($this->currentUser()->isAuthenticated()) {
diff --git a/core/modules/system/config/system.form.yml b/core/modules/system/config/system.form.yml
new file mode 100644
index 0000000..5e7a519
--- /dev/null
+++ b/core/modules/system/config/system.form.yml
@@ -0,0 +1 @@
+cache_expire: '21600'
diff --git a/core/modules/system/lib/Drupal/system/Tests/Form/FormCacheTest.php b/core/modules/system/lib/Drupal/system/Tests/Form/FormCacheTest.php
index 0e6d629..bf9ee3e 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Form/FormCacheTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Form/FormCacheTest.php
@@ -34,6 +34,9 @@ public function setUp() {
     parent::setUp();
     $this->installSchema('system', array('key_value_expire'));
 
+    // Only a minimal config is loaded, so set cache timeout explicitly.
+    \Drupal::config('system.form')->set('cache_expire', 21600)->save();
+
     $this->form_build_id = $this->randomName();
     $this->form = array(
       '#property' => $this->randomName(),