diff --git a/captcha.install b/captcha.install
index 45da77c..1a15483 100755
--- a/captcha.install
+++ b/captcha.install
@@ -173,7 +173,8 @@ if (!empty($entity_ids) && is_array($entity_ids)) {
  * Handle and delete "add_captcha_description".
  */
 function captcha_update_8903(&$sandbox) {
-  $config = \Drupal::config('captcha.settings');
+  $config_factory = \Drupal::configFactory();
+  $config = $config_factory->getEditable('captcha.settings');
   $addDescription = $config->get('add_captcha_description');
   // If description was disabled before, set 'description' to an empty string,
   // so it is disabled again in the newest version:
@@ -181,5 +182,5 @@ function captcha_update_8903(&$sandbox) {
     $config->set('description', '')->save();
   }
   // Delete old config:
-  $config->delete('add_captcha_description')->save();
+  $config->clear('add_captcha_description')->save();
 }