diff --git a/captcha.module b/captcha.module
index 8634393..05dc38e 100755
--- a/captcha.module
+++ b/captcha.module
@@ -142,17 +142,24 @@ function captcha_form_alter(array &$form, FormStateInterface $form_state, $form_
   // Visitor does not have permission to skip CAPTCHAs.
   module_load_include('inc', 'captcha');
   if (!$account->hasPermission('skip CAPTCHA')) {
-
     /* @var CaptchaPoint $captcha_point */
     $captcha_point = \Drupal::entityTypeManager()
       ->getStorage('captcha_point')
       ->load($form_id);
 
+    $captcha_type = '';
+    if ($config->get('default_challenge_on_nonlisted_forms')) {
+      $captcha_type = $config->get('default_challenge');
+    }
     if ($captcha_point && $captcha_point->status()) {
+      $captcha_type = $captcha_point->getCaptchaType();
+    }
+
+    if (!empty($captcha_type)) {
       // Build CAPTCHA form element.
       $captcha_element = [
         '#type' => 'captcha',
-        '#captcha_type' => $captcha_point->getCaptchaType(),
+        '#captcha_type' => $captcha_type,
       ];
 
       // Add a CAPTCHA description if required.
diff --git a/config/install/captcha.settings.yml b/config/install/captcha.settings.yml
index ac797b0..2bfaaac 100755
--- a/config/install/captcha.settings.yml
+++ b/config/install/captcha.settings.yml
@@ -1,5 +1,6 @@
 default_challenge: 'captcha/Math'
 description: 'This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.'
+default_challenge_on_nonlisted_forms: false
 administration_mode: false
 allow_on_admin_pages: false
 add_captcha_description: true
diff --git a/config/schema/captcha.settings.yml b/config/schema/captcha.settings.yml
index 3cdcddb..1033517 100755
--- a/config/schema/captcha.settings.yml
+++ b/config/schema/captcha.settings.yml
@@ -7,10 +7,13 @@ captcha.settings:
   mapping:
     default_challenge:
       type: string
-      label: 'The default challenge for captcha.'
+      label: 'The default challenge for CAPTCHA.'
     description:
       type: label
       label: 'The default captcha description.'
+    default_challenge_on_nonlisted_forms:
+      type: boolean
+      label: 'Add default challenge of CAPTCHA to all forms.'
     administration_mode:
       type: boolean
       label: 'Add CAPTCHA administration links to forms'
diff --git a/src/Form/CaptchaSettingsForm.php b/src/Form/CaptchaSettingsForm.php
index 24eb912..dde6b30 100755
--- a/src/Form/CaptchaSettingsForm.php
+++ b/src/Form/CaptchaSettingsForm.php
@@ -82,6 +82,13 @@ class CaptchaSettingsForm extends ConfigFormBase {
       '#default_value' => $config->get('default_challenge'),
     ];
 
+    $form['form_protection']['default_challenge_on_nonlisted_forms'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Default challenge on non-listed forms.'),
+      '#default_value' => $config->get('default_challenge_on_nonlisted_forms'),
+      '#description' => $this->t('Normally, no challenge is added to forms that are not listed above. Enabling this option will add the default challenge instead.'),
+    ];
+
     // Field for the CAPTCHA administration mode.
     $form['form_protection']['administration_mode'] = [
       '#type' => 'checkbox',
@@ -89,6 +96,7 @@ class CaptchaSettingsForm extends ConfigFormBase {
       '#default_value' => $config->get('administration_mode'),
       '#description' => $this->t('This option makes it easy to manage CAPTCHA settings on forms. When enabled, users with the <em>administer CAPTCHA settings</em> permission will see a fieldset with CAPTCHA administration links on all forms, except on administrative pages.'),
     ];
+
     // Field for the CAPTCHAs on admin pages.
     $form['form_protection']['allow_on_admin_pages'] = [
       '#type' => 'checkbox',
@@ -203,6 +211,7 @@ class CaptchaSettingsForm extends ConfigFormBase {
     $config->set('administration_mode', $form_state->getValue('administration_mode'));
     $config->set('allow_on_admin_pages', $form_state->getValue('allow_on_admin_pages'));
     $config->set('default_challenge', $form_state->getValue('default_challenge'));
+    $config->set('default_challenge_on_nonlisted_forms', $form_state->getValue('default_challenge_on_nonlisted_forms'));
 
     // CAPTCHA description stuff.
     $config->set('add_captcha_description', $form_state->getValue('add_captcha_description'));