diff --git a/core/lib/Drupal/Core/Form/FormErrorInterface.php b/core/lib/Drupal/Core/Form/FormErrorInterface.php
index c642ed3..e203908 100644
--- a/core/lib/Drupal/Core/Form/FormErrorInterface.php
+++ b/core/lib/Drupal/Core/Form/FormErrorInterface.php
@@ -92,15 +92,15 @@
    * would be triggered if the input processing and validation steps were fully
    * skipped.
    *
-   * @param $name
+   * @param string $name
    *   The name of the form element. If the #parents property of your form
    *   element is array('foo', 'bar', 'baz') then you may set an error on 'foo'
    *   or 'foo][bar][baz'. Setting an error on 'foo' sets an error for every
    *   element where the #parents array starts with 'foo'.
    * @param array $form_state
    *   An associative array containing the current state of the form.
-   * @param $message
-   *   The error message to present to the user.
+   * @param string $message
+   *   (optional) The error message to present to the user.
    *
    * @return mixed
    *   Return value is for internal use only. To get a list of errors, use
diff --git a/core/modules/search/lib/Drupal/search/Form/SearchBlockForm.php b/core/modules/search/lib/Drupal/search/Form/SearchBlockForm.php
index eadc2dd..c943c93 100644
--- a/core/modules/search/lib/Drupal/search/Form/SearchBlockForm.php
+++ b/core/modules/search/lib/Drupal/search/Form/SearchBlockForm.php
@@ -72,7 +72,7 @@ public function submitForm(array &$form, array &$form_state) {
       );
     }
     else {
-      $this->setFormError(NULL, $form_state, $this->t('Search is currently disabled.'), 'error');
+      $this->setFormError('', $form_state, $this->t('Search is currently disabled.'), 'error');
     }
   }
 }