diff --git a/captcha.module b/captcha.module
index fde54e7..fc8248e 100644
--- a/captcha.module
+++ b/captcha.module
@@ -10,6 +10,7 @@
  */
 
 use Drupal\captcha\Entity\CaptchaPoint;
+use Drupal\Core\Form\FormStateInterface;
 
 /**
  * Constants for CAPTCHA persistence.
@@ -18,6 +19,7 @@ use Drupal\captcha\Entity\CaptchaPoint;
  * form saves them as strings in the variables table anyway?
  */
 
+// @TODO: move all constants to some class.
 // Always add a CAPTCHA (even on every page of a multipage workflow).
 define('CAPTCHA_PERSISTENCE_SHOW_ALWAYS', 0);
 // Only one CAPTCHA has to be solved per form instance/multi-step workflow.
@@ -146,7 +148,7 @@ function captcha_element_info() {
 /**
  * Process callback for CAPTCHA form element.
  */
-function captcha_element_process(array $element, array &$form_state, array $complete_form) {
+function captcha_element_process(array $element, FormStateInterface $form_state, array $complete_form) {
   // Add captcha.inc file
   module_load_include('inc', 'captcha');
 
@@ -300,8 +302,9 @@ function theme_captcha($variables) {
  * if needed and adds. CAPTCHA administration links for site
  * administrators if this option is enabled.
  */
-function captcha_form_alter(array &$form, array &$form_state, $form_id) {
-  if (!user_access('skip CAPTCHA')) {
+function captcha_form_alter(array &$form, FormStateInterface $form_state, $form_id) {
+  $account = \Drupal::currentUser();
+  if (!$account->hasPermission('skip CAPTCHA')) {
     // Visitor does not have permission to skip CAPTCHAs.
     module_load_include('inc', 'captcha');
 
@@ -327,8 +330,8 @@ function captcha_form_alter(array &$form, array &$form_state, $form_id) {
     }
   }
   elseif (\Drupal::config('captcha.settings')->get('captcha_administration_mode', FALSE)
-    && user_access('administer CAPTCHA settings')
-    && (arg(0) != 'admin' || \Drupal::config('captcha.settings')->get('captcha_allow_on_admin_pages', FALSE))) {
+    && $account->hasPermission('administer CAPTCHA settings')
+    && (\Drupal::service('router.admin_context')->isAdminRoute()  || \Drupal::config('captcha.settings')->get('captcha_allow_on_admin_pages', FALSE))) {
     // Add CAPTCHA administration tools.
     module_load_include('inc', 'captcha');
 
@@ -358,25 +361,25 @@ function captcha_form_alter(array &$form, array &$form_state, $form_id) {
           '@disable' => url("admin/config/people/captcha/captcha-points/$form_id/disable", array('query' => drupal_get_destination())),
         )),
       );
-      // Add an example challenge with solution.
-      // This does not work with the reCAPTCHA and Egglue challenges as
-      // discussed in http://drupal.org/node/487032 and
-      // http://drupal.org/node/525586. As a temporary workaround, we
-      // blacklist the reCAPTCHA and Egglue challenges and do not show
-      // an example challenge.
-      // TODO: Once the issues mentioned above are fixed, this workaround
-      // should be removed.
-      $captcha_element['example'] = array(
-        '#type' => 'details',
-        '#title' => t('Example'),
-        '#description' => t('This is a pre-solved, non-blocking example of this challenge.'),
-        '#open' => TRUE,
-      );
-      $captcha_element['example']['example_captcha'] = array(
-        '#type' => 'captcha',
-        '#captcha_type' => $captcha_point->getCaptchaType(),
-        '#captcha_admin_mode' => TRUE,
-      );
+//      // Add an example challenge with solution.
+//      // This does not work with the reCAPTCHA and Egglue challenges as
+//      // discussed in http://drupal.org/node/487032 and
+//      // http://drupal.org/node/525586. As a temporary workaround, we
+//      // blacklist the reCAPTCHA and Egglue challenges and do not show
+//      // an example challenge.
+//      // TODO: Once the issues mentioned above are fixed, this workaround
+//      // should be removed.
+//      $captcha_element['example'] = array(
+//        '#type' => 'details',
+//        '#title' => t('Example'),
+//        '#description' => t('This is a pre-solved, non-blocking example of this challenge.'),
+//        '#open' => TRUE,
+//      );
+//      $captcha_element['example']['example_captcha'] = array(
+//        '#type' => 'captcha',
+//        '#captcha_type' => $captcha_point->getCaptchaType(),
+//        '#captcha_admin_mode' => TRUE,
+//      );
     }
     else {
       $captcha_element['#title'] = t('CAPTCHA: no challenge enabled');
@@ -492,7 +495,7 @@ function captcha_validate_case_insensitive_ignore_spaces($solution, $response) {
  *   Array with $posted_form_id and $post_captcha_sid (with NULL values
  *   if the values could not be found, e.g. for a fresh form).
  */
-function _captcha_get_posted_captcha_info(array $element, array $form_state, $this_form_id) {
+function _captcha_get_posted_captcha_info(array $element, FormStateInterface $form_state, $this_form_id) {
   if ($form_state['submitted'] && isset($form_state['captcha_info'])) {
     // We are handling (or rebuilding) an already submitted form,
     // so we already determined the posted form ID and CAPTCHA session ID
diff --git a/captcha.routing.yml b/captcha.routing.yml
index 05695df..4f5ab8a 100644
--- a/captcha.routing.yml
+++ b/captcha.routing.yml
@@ -2,6 +2,7 @@ captcha_settings:
   path: '/admin/config/people/captcha'
   defaults:
     _form: '\Drupal\captcha\Form\CaptchaSettingsForm'
+    _title: 'CAPTCHA settings'
   requirements:
     _permission: 'administer CAPTCHA settings'
 
diff --git a/image_captcha/config/install/image_captcha.settings.yml b/image_captcha/config/install/image_captcha.settings.yml
index 0185911..a08ce49 100644
--- a/image_captcha/config/install/image_captcha.settings.yml
+++ b/image_captcha/config/install/image_captcha.settings.yml
@@ -1,5 +1,5 @@
 image_captcha_fonts_preview_map_cache: []
-image_captcha_fonts: []
+image_captcha_fonts: ['BUILTIN']
 image_captcha_font_size: 30
 image_captcha_character_spacing: '1.2'
 image_captcha_image_allowed_chars: 'aAbBCdEeFfGHhijKLMmNPQRrSTtWXYZ23456789'
diff --git a/image_captcha/image_captcha.routing.yml b/image_captcha/image_captcha.routing.yml
index 9f3e653..48ef56e 100644
--- a/image_captcha/image_captcha.routing.yml
+++ b/image_captcha/image_captcha.routing.yml
@@ -8,13 +8,13 @@ image_captcha.settings:
 image_captcha.font_preview:
   path: '/admin/config/people/captcha/image_captcha/font_preview/{token}'
   defaults:
-    _controller: '\Drupal\image_captcha\Controller\CaptchaFontPreview'
+    _controller: '\Drupal\image_captcha\Controller\CaptchaFontPreview::content'
   requirements:
     _permission: 'administer CAPTCHA settings'
 
 image_captcha.generator:
   path: '/image-captcha-generate/{session_id}/{timestamp}'
   defaults:
-    _content: '\Drupal\image_captcha\Controller\CaptchaImageGenerator::send'
+    _controller: '\Drupal\image_captcha\Controller\CaptchaImageGenerator::create'
   requirements:
     _permission: 'access content'
diff --git a/image_captcha/src/Controller/CaptchaFontPreview.php b/image_captcha/src/Controller/CaptchaFontPreview.php
index d494f65..38b7c7d 100644
--- a/image_captcha/src/Controller/CaptchaFontPreview.php
+++ b/image_captcha/src/Controller/CaptchaFontPreview.php
@@ -7,14 +7,14 @@
 
 namespace Drupal\image_captcha\Controller;
 
-use Drupal\Core\Controller\HtmlPageController;
 use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\StreamedResponse;
 
-class CaptchaFontPreview extends HtmlPageController {
+class CaptchaFontPreview extends StreamedResponse {
   /**
    * {@inheritdoc}
    */
-  public function content(Request $request, $_content) {
+  public function content(Request $request) {
     $token = $request->get('token');
     // Get the font from the given font token.
     if ($token == 'BUILTIN') {
diff --git a/image_captcha/src/Controller/CaptchaImageGenerator.php b/image_captcha/src/Controller/CaptchaImageGenerator.php
index c049a83..1a905f5 100644
--- a/image_captcha/src/Controller/CaptchaImageGenerator.php
+++ b/image_captcha/src/Controller/CaptchaImageGenerator.php
@@ -49,10 +49,10 @@ class CaptchaImageGenerator extends StreamedResponse {
    */
   public function sendHeaders() {
     if ($this->config->get('image_captcha_file_format') == IMAGE_CAPTCHA_FILE_FORMAT_JPG) {
-      header('Content-Type: image/jpeg');
+      $this->headers->set('content-type', 'image/jpeg');
     }
     else {
-      header('Content-Type: image/png');
+      $this->headers->set('content-type', 'image/png');
     }
 
     return parent::sendHeaders();
@@ -63,6 +63,9 @@ class CaptchaImageGenerator extends StreamedResponse {
       return;
     }
 
+    // Begin capturing the byte stream
+    ob_start();
+
     $file_format = $this->config->get('image_captcha_file_format');
     if ($file_format == IMAGE_CAPTCHA_FILE_FORMAT_JPG) {
       imagejpeg($this->image);
@@ -107,7 +110,7 @@ class CaptchaImageGenerator extends StreamedResponse {
   protected function generateImage($code) {
     $fonts = _image_captcha_get_enabled_fonts();
 
-    $font_size = (int) $this->config->get('image_captcha_font_size');
+    $font_size = $this->config->get('image_captcha_font_size');
     list($width, $height) = _image_captcha_image_size($code);
 
     $image = imagecreatetruecolor($width, $height);
@@ -124,12 +127,12 @@ class CaptchaImageGenerator extends StreamedResponse {
       imagecolortransparent($image, $background_color);
     }
     imagefilledrectangle($image, 0, 0, $width, $height, $background_color);
+//
+//    // Do we need to draw in RTL mode?
+//    global $language;
+//    $rtl = $language->direction && ((bool) $this->config->get('image_captcha_rtl_support'));
 
-    // Do we need to draw in RTL mode?
-    global $language;
-    $rtl = $language->direction && ((bool) $this->config->get('image_captcha_rtl_support'));
-
-    $result = $this->printString($image, $width, $height, $fonts, $font_size, $code, $rtl);
+    $result = $this->printString($image, $width, $height, $fonts, $font_size, $code);
     if (!$result) {
       return FALSE;
     }
@@ -310,9 +313,11 @@ class CaptchaImageGenerator extends StreamedResponse {
     $character_quantity = count($characters);
 
     $foreground_rgb = $this->hexToRgb($this->config->get('image_captcha_foreground_color'));
+    $background_rgb = $this->hexToRgb($this->config->get('image_captcha_background_color'));
+    $background_color = imagecolorallocate($image, $background_rgb[0], $background_rgb[1], $background_rgb[2]);
     $foreground_color = imagecolorallocate($image, $foreground_rgb[0], $foreground_rgb[1], $foreground_rgb[2]);
     // Precalculate the value ranges for color randomness.
-    $foreground_randomness = (int) $this->config->get('image_captcha_foreground_color_randomness');
+    $foreground_randomness = $this->config->get('image_captcha_foreground_color_randomness');
     $foreground_color_range = array();
 
     if ($foreground_randomness) {
@@ -345,6 +350,7 @@ class CaptchaImageGenerator extends StreamedResponse {
 
       // Get character dimensions for TrueType fonts.
       if ($font != 'BUILTIN') {
+        putenv('GDFONTPATH=' . realpath('.'));
         $bbox = imagettfbbox($font_size, 0, drupal_realpath($font), $character);
         // In very rare cases with some versions of the GD library, the x-value
         // of the left side of the bounding box as returned by the first call of
diff --git a/image_captcha/src/Form/ImageCaptchaSettingsForm.php b/image_captcha/src/Form/ImageCaptchaSettingsForm.php
index 2fd4016..b8949a2 100644
--- a/image_captcha/src/Form/ImageCaptchaSettingsForm.php
+++ b/image_captcha/src/Form/ImageCaptchaSettingsForm.php
@@ -8,6 +8,7 @@
 namespace Drupal\image_captcha\Form;
 
 use Drupal\Core\Form\ConfigFormBase;
+use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Language\Language;
 
 /**
@@ -25,7 +26,8 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $config = $this->config('image_captcha.settings');
     // Add CSS and JS for theming and added usability on admin form.
     $form['#attached']['library'][] = 'captcha_image/base';
 
@@ -61,13 +63,13 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
     $form['image_captcha_code_settings']['image_captcha_image_allowed_chars'] = array(
       '#type' => 'textfield',
       '#title' => t('Characters to use in the code'),
-      '#default_value' => $this->config('image_captcha_image_allowed_chars'),
+      '#default_value' => $config->get('image_captcha_image_allowed_chars'),
     );
     $form['image_captcha_code_settings']['image_captcha_code_length'] = array(
       '#type' => 'select',
       '#title' => t('Code length'),
       '#options' => array(2 => 2, 3, 4, 5, 6, 7, 8, 9, 10),
-      '#default_value' => (int) $this->config('image_captcha_code_length'),
+      '#default_value' => $config->get('image_captcha_code_length'),
       '#description' => t('The code length influences the size of the image. Note that larger values make the image generation more CPU intensive.'),
     );
     // RTL support option (only show this option when there are RTL languages).
@@ -76,7 +78,7 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
       $form['image_captcha_code_settings']['image_captcha_rtl_support'] = array(
         '#title' => t('RTL support'),
         '#type' => 'checkbox',
-        '#default_value' => $this->config('image_captcha_rtl_support'),
+        '#default_value' => $config->get('image_captcha_rtl_support'),
         '#description' => t('Enable this option to render the code from right to left for right to left languages.'),
       );
     }
@@ -95,7 +97,7 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
       '#type' => 'textfield',
       '#title' => t('Background color'),
       '#description' => t('Enter the hexadecimal code for the background color (e.g. #FFF or #FFCE90). When using the PNG file format with transparent background, it is recommended to set this close to the underlying background color.'),
-      '#default_value' => $this->config('image_captcha_background_color'),
+      '#default_value' => $config->get('image_captcha_background_color'),
       '#maxlength' => 7,
       '#size' => 8,
     );
@@ -103,7 +105,7 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
       '#type' => 'textfield',
       '#title' => t('Text color'),
       '#description' => t('Enter the hexadecimal code for the text color (e.g. #000 or #004283).'),
-      '#default_value' => $this->config('image_captcha_foreground_color', '#000000'),
+      '#default_value' => $config->get('image_captcha_foreground_color'),
       '#maxlength' => 7,
       '#size' => 8,
     );
@@ -117,14 +119,14 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
         150 => t('High variation'),
         200 => t('Very high variation'),
       ),
-      '#default_value' => (int) $this->config('image_captcha_foreground_color_randomness'),
+      '#default_value' => $config->get('image_captcha_foreground_color_randomness'),
       '#description' => t('The different characters will have randomized colors in the specified range around the text color.'),
     );
     $form['image_captcha_color_settings']['image_captcha_file_format'] = array(
       '#type' => 'select',
       '#title' => t('File format'),
       '#description' => t('Select the file format for the image. JPEG usually results in smaller files, PNG allows tranparency.'),
-      '#default_value' => $this->config('image_captcha_file_format'),
+      '#default_value' => $config->get('image_captcha_file_format'),
       '#options' => array(
         IMAGE_CAPTCHA_FILE_FORMAT_JPG => t('JPEG'),
         IMAGE_CAPTCHA_FILE_FORMAT_PNG => t('PNG'),
@@ -155,27 +157,27 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
         9 => '9',
         10 => t('@level - high', array('@level' => '10')),
       ),
-      '#default_value' => (int) $this->config('image_captcha_distortion_amplitude'),
+      '#default_value' => $config->get('image_captcha_distortion_amplitude'),
       '#description' => t('Set the degree of wave distortion in the image.'),
     );
     $form['image_captcha_distortion_and_noise']['image_captcha_bilinear_interpolation'] = array(
       '#type' => 'checkbox',
       '#title' => t('Smooth distortion'),
-      '#default_value' => $this->config('image_captcha_bilinear_interpolation'),
+      '#default_value' => $config->get('image_captcha_bilinear_interpolation'),
       '#description' => t('This option enables bilinear interpolation of the distortion which makes the image look smoother, but it is more CPU intensive.'),
     );
 
     $form['image_captcha_distortion_and_noise']['image_captcha_dot_noise'] = array(
       '#type' => 'checkbox',
       '#title' => t('Add salt and pepper noise'),
-      '#default_value' => $this->config('image_captcha_dot_noise'),
+      '#default_value' => $config->get('image_captcha_dot_noise'),
       '#description' => t('This option adds randomly colored point noise.'),
     );
 
     $form['image_captcha_distortion_and_noise']['image_captcha_line_noise'] = array(
       '#type' => 'checkbox',
       '#title' => t('Add line noise'),
-      '#default_value' => $this->config('image_captcha_line_noise', 0),
+      '#default_value' => $config->get('image_captcha_line_noise', 0),
       '#description' => t('This option enables lines randomly drawn on top of the text code.'),
     );
 
@@ -191,7 +193,7 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
         7 => '7',
         10 => '10 - ' . t('severe'),
       ),
-      '#default_value' => (int) $this->config('image_captcha_noise_level'),
+      '#default_value' => (int) $config->get('image_captcha_noise_level'),
     );
 
     return parent::buildForm($form, $form_state);
@@ -200,7 +202,7 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
   /**
    * {@inheritdoc}
    */
-  public function validateForm(array &$form, array &$form_state) {
+  public function validateForm(array &$form, FormStateInterface $form_state) {
 
     // Check image_captcha_image_allowed_chars for spaces.
     if (preg_match('/\s/', $form_state['values']['image_captcha_image_allowed_chars'])) {
@@ -240,11 +242,11 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {
+  public function submitForm(array &$form, FormStateInterface $form_state) {
     if (!isset($form['image_captcha_font_settings']['no_ttf_support'])) {
       // Filter the image_captcha fonts array to pick out the selected ones.
       $fonts = array_filter($form_state['values']['image_captcha_fonts']);
-      $this->config('image_captcha_fonts', $fonts);
+      $this->config('image_captcha.settings')->set('image_captcha_fonts', $fonts)->save();
     }
 
     parent::SubmitForm($form, $form_state);
@@ -261,6 +263,7 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
    *   The font settings specific form elements.
    */
   protected function settingsDotSection() {
+    $config = $this->config('image_captcha.settings');
     // Put it all in a details element.
     $form = array(
       '#type' => 'details',
@@ -286,7 +289,7 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
       // Cache the list of previewable fonts. All the previews are done
       // in separate requests, and we don't want to rescan the filesystem
       // every time, so we cache the result.
-      $this->config('image_captcha_fonts_preview_map_cache', $fonts);
+      $config->get('image_captcha_fonts_preview_map_cache', $fonts);
       // Put these fonts with preview image in the list.
       foreach ($fonts as $token => $font) {
         $img_src = check_url(url('admin/config/people/captcha/image_captcha/font_preview/' . $token));
@@ -330,7 +333,7 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
           48 => '48 pt',
           64 => '64 pt - ' . t('extra large'),
         ),
-        '#default_value' => (int) $this->config('image_captcha_font_size'),
+        '#default_value' => (int) $config->get('image_captcha_font_size'),
         '#description' => t('The font size influences the size of the image. Note that larger values make the image generation more CPU intensive.'),
       );
     }
@@ -341,7 +344,7 @@ class ImageCaptchaSettingsForm extends ConfigFormBase {
       '#type' => 'select',
       '#title' => t('Character spacing'),
       '#description' => t('Define the average spacing between characters. Note that larger values make the image generation more CPU intensive.'),
-      '#default_value' => $this->config('image_captcha_character_spacing'),
+      '#default_value' => $config->get('image_captcha_character_spacing'),
       '#options' => array(
         '0.75' => t('tight'),
         '1' => t('normal'),
diff --git a/src/Form/CaptchaExamplesForm.php b/src/Form/CaptchaExamplesForm.php
index 48f5faf..244e6b6 100644
--- a/src/Form/CaptchaExamplesForm.php
+++ b/src/Form/CaptchaExamplesForm.php
@@ -9,6 +9,7 @@ namespace Drupal\captcha\Form;
 
 use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\Form\ConfigFormBase;
+use Drupal\Core\Form\FormStateInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
@@ -46,7 +47,7 @@ class CaptchaExamplesForm extends ConfigFormBase {
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
     module_load_include('inc', 'captcha', 'captcha.admin');
 
     $module = $this->getRequest()->get('module');
diff --git a/src/Form/CaptchaPointDeleteForm.php b/src/Form/CaptchaPointDeleteForm.php
index 48c0271..953a01d 100644
--- a/src/Form/CaptchaPointDeleteForm.php
+++ b/src/Form/CaptchaPointDeleteForm.php
@@ -34,7 +34,7 @@ class CaptchaPointDeleteForm extends EntityConfirmFormBase {
   /**
    * {@inheritdoc}
    */
-  public function submit(array $form, array &$form_state) {
+  public function submit(array $form, FormStateInterface $form_state) {
     $this->entity->delete();
     drupal_set_message($this->t('Category %label has been deleted.', array('%label' => $this->entity->label())));
     $form_state['redirect_route'] = $this->getCancelRoute();
diff --git a/src/Form/CaptchaPointForm.php b/src/Form/CaptchaPointForm.php
index 306af3a..a3d264b 100644
--- a/src/Form/CaptchaPointForm.php
+++ b/src/Form/CaptchaPointForm.php
@@ -9,13 +9,14 @@ namespace Drupal\captcha\Form;
 
 use Drupal\Core\Entity\EntityForm;
 use Drupal\captcha\CaptchaPointInterface;
+use Drupal\Core\Form\FormStateInterface;
 
 class CaptchaPointForm extends EntityForm {
 
   /**
    * {@inheritdoc}
    */
-  public function form(array $form, array &$form_state) {
+  public function form(array $form, FormStateInterface $form_state) {
     $form = parent::form($form, $form_state);
 
     module_load_include('inc', 'captcha', 'captcha.admin');
@@ -53,7 +54,7 @@ class CaptchaPointForm extends EntityForm {
   /**
    * {@inheritdoc}
    */
-  public function save(array $form, array &$form_state) {
+  public function save(array $form, FormStateInterface $form_state) {
     $captcha_point = $this->entity;
     $status = $captcha_point->save();
     if ($status) {
diff --git a/src/Form/CaptchaSettingsForm.php b/src/Form/CaptchaSettingsForm.php
index d6e55de..7a81510 100644
--- a/src/Form/CaptchaSettingsForm.php
+++ b/src/Form/CaptchaSettingsForm.php
@@ -9,6 +9,7 @@ namespace Drupal\captcha\Form;
 
 use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\Form\ConfigFormBase;
+use Drupal\Core\Form\FormStateInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
@@ -46,7 +47,7 @@ class CaptchaSettingsForm extends ConfigFormBase {
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
     $config = $this->config('captcha.settings');
     module_load_include('inc', 'captcha');
     module_load_include('inc', 'captcha', 'captcha.admin');
@@ -106,7 +107,7 @@ class CaptchaSettingsForm extends ConfigFormBase {
       '#default_value' => $config->get('captcha_add_captcha_description'),
     );
     // Textfield(s) for the CAPTCHA description.
-    if (module_exists('locale')) {
+    if (\Drupal::moduleHandler()->moduleExists('locale')) {
       $langs = language_list();
       $form['captcha_descriptions'] = array(
         '#type' => 'details',
@@ -194,7 +195,7 @@ class CaptchaSettingsForm extends ConfigFormBase {
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {
+  public function submitForm(array &$form, FormStateInterface $form_state) {
     $config = \Drupal::config('captcha.settings');
     $config->set('captcha_administration_mode', $form_state['values']['captcha_administration_mode']);
     $config->set('captcha_allow_on_admin_pages', $form_state['values']['captcha_allow_on_admin_pages']);
@@ -203,7 +204,7 @@ class CaptchaSettingsForm extends ConfigFormBase {
     // CAPTCHA description stuff.
     $config->set('captcha_add_captcha_description', $form_state['values']['captcha_add_captcha_description']);
     // Save (or reset) the CAPTCHA descriptions.
-    if (module_exists('locale')) {
+    if (\Drupal::moduleHandler()->moduleExists('locale')) {
       $langs = language_list();
       foreach ($langs as $lang_code => $lang_name) {
         $description = $form_state['values']["captcha_description_$lang_code"];
@@ -242,10 +243,10 @@ class CaptchaSettingsForm extends ConfigFormBase {
    *
    * @param array $form
    *   Form structured array.
-   * @param array $form_state
+   * @param FormStateInterface  $form_state
    *   Form state strutured array.
    */
-  public function captchaClearCaptchaPlacementCacheSubmit(array $form, array $form_state) {
+  public function captchaClearCaptchaPlacementCacheSubmit(array $form, FormStateInterface  $form_state) {
     $this->state->delete('captcha_placement_map_cache');
     drupal_set_message($this->t('Cleared the CAPTCHA placement cache.'));
   }