diff --git a/src/EventSubscriber/ConfigDevelSubscriberBase.php b/src/EventSubscriber/ConfigDevelSubscriberBase.php
index 5942a94..0ab70ec 100644
--- a/src/EventSubscriber/ConfigDevelSubscriberBase.php
+++ b/src/EventSubscriber/ConfigDevelSubscriberBase.php
@@ -74,7 +74,7 @@ class ConfigDevelSubscriberBase {
    * @return \Drupal\Core\Config\Config
    */
   protected function getSettings() {
-    return $this->configFactory->get('config_devel.settings');
+    return $this->configFactory->getEditable('config_devel.settings');
   }
 
 }
diff --git a/src/Form/ConfigDevelSettingsForm.php b/src/Form/ConfigDevelSettingsForm.php
index 6914b92..3de5142 100644
--- a/src/Form/ConfigDevelSettingsForm.php
+++ b/src/Form/ConfigDevelSettingsForm.php
@@ -18,7 +18,7 @@ use Drupal\Core\Form\FormStateInterface;
 class ConfigDevelSettingsForm extends ConfigFormBase {
 
   /**
-   * @var \Drupal\Core\Config\Config
+   * @var \Drupal\Core\Config\ConfigFactoryInterface
    */
   protected $config;
 
@@ -31,7 +31,7 @@ class ConfigDevelSettingsForm extends ConfigFormBase {
    * {@inheritdoc}
    */
   public function buildForm(array $form, FormStateInterface $form_state) {
-    $this->config = $this->configFactory()->get('config_devel.settings');
+    $this->config = $this->configFactory()->getEditable('config_devel.settings');
     $default_value = '';
     foreach ($this->config->get('auto_import') as $file) {
       $default_value .= $file['filename'] . "\n";
@@ -56,9 +56,9 @@ class ConfigDevelSettingsForm extends ConfigFormBase {
    */
   public function validateForm(array &$form, FormStateInterface $form_state) {
     foreach (array('auto_import', 'auto_export') as $key) {
-      $form_state['values'][$key] = array_filter(preg_split("/\r\n/", $form_state->getValues()[$key]));
+      $form_state->setValue($key, array_filter(preg_split("/\r\n/", $form_state->getValues()[$key])));
     }
-    foreach ($form_state['values']['auto_import'] as $file) {
+    foreach ($form_state->getValues()['auto_import'] as $file) {
       $name = basename($file, '.' . FileStorage::getFileExtension());
       if (in_array($name, array('system.site', 'core.extension', 'simpletest.settings'))) {
         $this->setFormError($this->t('@name is not compatible with this module', array('@name' => $name)), $form_state);
@@ -93,4 +93,10 @@ class ConfigDevelSettingsForm extends ConfigFormBase {
     return 'config_devel_settings';
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected function getEditableConfigNames() {
+    return [];
+  }
 }