diff --git a/core/modules/user/src/AccountForm.php b/core/modules/user/src/AccountForm.php
index 14272a2..2b33726 100644
--- a/core/modules/user/src/AccountForm.php
+++ b/core/modules/user/src/AccountForm.php
@@ -391,15 +391,13 @@ public function submitForm(array &$form, FormStateInterface $form_state) {
       // Send a verification to the new email address.
       $account_cloned = clone $account;
       $account_cloned->setEmail($new_mail);
-      if (_user_mail_notify('mail_change_verification', $account_cloned)) {
+      if (_user_mail_notify('mail_change_verification', $account_cloned) !== NULL) {
         // Send notification email to the old email address.
         _user_mail_notify('mail_change_notification', $account);
+        // The user's mail address will be updated only after verification.
+        $form_state->setValue('mail', $old_mail);
+        drupal_set_message($this->t('Your new email address needs to be validated. Further instructions have been sent to your new email address.'), 'warning');
       }
-
-      // The user's mail address will be updated only after verification.
-      $form_state->setValue('mail', $old_mail);
-
-      drupal_set_message($this->t('Your new email address needs to be validated. Further instructions have been sent to your new email address.'), 'warning');
     }
 
     parent::submitForm($form, $form_state);
diff --git a/core/modules/user/user.module b/core/modules/user/user.module
index 7b0f1a1..79a137e 100644
--- a/core/modules/user/user.module
+++ b/core/modules/user/user.module
@@ -1199,11 +1199,13 @@ function user_role_revoke_permissions($rid, array $permissions = array()) {
  *   (optional) Language code to use for the notification, overriding account
  *   language.
  *
- * @return array
- *   An array containing various information about the message.
- *   See \Drupal\Core\Mail\MailManagerInterface::mail() for details.
+ * @return array|null
+ *   An array containing various information about the message, as they are
+ *   returned by \Drupal\Core\Mail\MailManagerInterface::mail(), or NULL if the
+ *   notifications for the required operation are disabled.
  *
  * @see user_mail_tokens()
+ * @see \Drupal\Core\Mail\MailManagerInterface::mail()
  */
 function _user_mail_notify($op, $account, $langcode = NULL) {
   if (\Drupal::config('user.settings')->get('notify.' . $op)) {