diff -u b/core/modules/system/system.install b/core/modules/system/system.install
--- b/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -1758,11 +1758,6 @@
     'cron_threshold_warning' => 'threshold.requirements_warning',
     'cron_threshold_error' => 'threshold.requirements_error',
   ));
-
-  if ($cron_key = update_variable_get('cron_key', FALSE)) {
-    state()->set('system.cron_key', $cron_key);
-  }
-  update_variable_del('cron_key');
 }
 
 /**
@@ -2204,6 +2199,15 @@
 }
 
 /**
+ * Moves cron_key from variable to state.
+ *
+ * @ingroup config_upgrade
+ */
+function system_update_8033() {
+  update_variables_to_state(array('cron_key' => 'system.cron_key'));
+}
+
+/**
  * @} End of "defgroup updates-7.x-to-8.x".
  * The next series of updates should start at 9000.
  */
only in patch2:
unchanged:
--- a/core/modules/system/lib/Drupal/system/Tests/Upgrade/StateSystemUpgradePathTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Upgrade/StateSystemUpgradePathTest.php
@@ -35,6 +35,10 @@ public function testSystemVariableUpgrade() {
 
     $expected_state = array();
 
+    $expected_state['system.cron_key'] = array(
+      'value' => 'kdm95qppDDlyZrcUOx453YwQqDA4DNmxi4VQcxzFU9M',
+      'variable_name' => 'cron_key',
+    );
     $expected_state['update.last_check'] = array(
       'value' => 1304208000,
       'variable_name' => 'update_last_check',
only in patch2:
unchanged:
--- a/core/modules/system/tests/upgrade/drupal-7.state.system.database.php
+++ b/core/modules/system/tests/upgrade/drupal-7.state.system.database.php
@@ -19,3 +19,7 @@
   ->key(array('name' => 'update_last_email_notification'))
   ->fields(array('value' => serialize(1304208000)))
   ->execute();
+db_merge('variable')
+  ->key(array('name' => 'cron_key'))
+  ->fields(array('value' => serialize('kdm95qppDDlyZrcUOx453YwQqDA4DNmxi4VQcxzFU9M')))
+  ->execute();