diff --git a/currency/src/Controller/CurrencyImportForm.php b/currency/src/Controller/CurrencyImportForm.php
index 68ead96..a743fe3 100644
--- a/currency/src/Controller/CurrencyImportForm.php
+++ b/currency/src/Controller/CurrencyImportForm.php
@@ -9,6 +9,7 @@ namespace Drupal\currency\Controller;
 
 use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
 use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\StringTranslation\TranslationInterface;
 use Drupal\Core\Url;
 use Drupal\currency\ConfigImporterInterface;
@@ -67,7 +68,7 @@ class CurrencyImportForm extends FormBase implements ContainerInjectionInterface
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
     $currencies = $this->configImporter->getImportableCurrencies();
     if (empty($currencies)) {
       $form['message'] = array(
@@ -104,17 +105,17 @@ class CurrencyImportForm extends FormBase implements ContainerInjectionInterface
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {
-    $currency = $this->configImporter->importCurrency($form_state['values']['currency_code']);
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $currency = $this->configImporter->importCurrency($form_state->getValues()['currency_code']);
     drupal_set_message($this->t('The %label has been imported.', array(
       '%label' => $currency->label(),
     )));
 
-    if ($form_state['triggering_element']['#name'] == 'import_edit') {
-      $form_state['redirect_route'] = $currency->urlInfo('edit-form');
+    if ($form_state->getTriggeringElement()['#name'] == 'import_edit') {
+      $form_state->setRedirectUrl($currency->urlInfo('edit-form'));
     }
     else {
-      $form_state['redirect_route'] = new Url('currency.currency.list');
+      $form_state->setRedirectUrl(new Url('currency.currency.list'));
     }
   }
 
diff --git a/currency/src/Controller/CurrencyLocaleImportForm.php b/currency/src/Controller/CurrencyLocaleImportForm.php
index 64aa58a..be58d27 100644
--- a/currency/src/Controller/CurrencyLocaleImportForm.php
+++ b/currency/src/Controller/CurrencyLocaleImportForm.php
@@ -9,6 +9,7 @@ namespace Drupal\currency\Controller;
 
 use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
 use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\StringTranslation\TranslationInterface;
 use Drupal\Core\Url;
 use Drupal\currency\ConfigImporterInterface;
@@ -67,7 +68,7 @@ class CurrencyLocaleImportForm extends FormBase implements ContainerInjectionInt
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
     $currency_locales = $this->configImporter->getImportableCurrencyLocales();
     if (empty($currency_locales)) {
       $form['message'] = array(
@@ -104,17 +105,17 @@ class CurrencyLocaleImportForm extends FormBase implements ContainerInjectionInt
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {
-    $currency_locale = $this->configImporter->importCurrencyLocale($form_state['values']['locale']);
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $currency_locale = $this->configImporter->importCurrencyLocale($form_state->getValues()['locale']);
     drupal_set_message($this->t('The %label has been imported.', array(
       '%label' => $currency_locale->label(),
     )));
 
-    if ($form_state['triggering_element']['#name'] == 'import_edit') {
-      $form_state['redirect_route'] = $currency_locale->urlInfo('edit-form');
+    if ($form_state->getTriggeringElement()['#name'] == 'import_edit') {
+      $form_state->setRedirectUrl($currency_locale->urlInfo('edit-form'));
     }
     else {
-      $form_state['redirect_route'] = new Url('currency.currency_locale.list');
+      $form_state->setRedirectUrl(new Url('currency.currency_locale.list'));
     }
   }