diff --git a/core/modules/system/lib/Drupal/system/Tests/Upgrade/MailUpgradePathTest.php b/core/modules/system/lib/Drupal/system/Tests/Upgrade/MailUpgradePathTest.php
index d52fd22..dff78a4 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Upgrade/MailUpgradePathTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Upgrade/MailUpgradePathTest.php
@@ -31,11 +31,11 @@ public function setUp() {
    * Tests that mail backends are upgraded to their Drupal 8 equivalents.
    */
   function testMailSystemUpgrade() {
-    variable_set('mail_system', array(
-      'default-system' => 'DefaultMailSystem',
+    $mail_interface_defaults = array(
+      'default' => 'Drupal\Core\Mail\PhpMail',
       'maillog' => 'MaillogMailSystem',
-    ));
-
+    );
+    config('system.mail')->set('interface', $mail_interface_defaults)->save();
     // Perform the upgrade without redirecting to check for pending updates,
     // so that we can test for user warnings.
     $this->performUpgrade(TRUE, FALSE);
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index b701cbf..788465b 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -2236,8 +2236,10 @@ function system_update_8047() {
         unset($old_mail_system_settings[$key]);
       }
     }
-    // Warn about non-core classes which may need to be updated.
-    drupal_set_message(t('The following mail backends need to be re-configured: @list', array('@list' => implode(', ', $old_mail_system_settings))), 'warning');
+    if (count($old_mail_system_settings)) {
+      // Warn about non-core classes which may need to be updated.
+      drupal_set_message(t('The following mail backends need to be re-configured: @list', array('@list' => implode(', ', $old_mail_system_settings))), 'warning');
+    }
 
     $new_mail_system_settings += $old_mail_system_settings;
     // Save the updated variable, and let update_variables_to_config convert it.