diff --git a/image_captcha/image_captcha.admin.inc b/image_captcha/image_captcha.admin.inc
index b3c9f02..4e3b5b9 100644
--- a/image_captcha/image_captcha.admin.inc
+++ b/image_captcha/image_captcha.admin.inc
@@ -10,7 +10,7 @@
 /**
  * Configuration form for image_captcha.
  */
-function image_captcha_settings_form() {
+function image_captcha_settings_form($form, &$form_state) {
 
   $form = array();
 
@@ -31,6 +31,14 @@ function image_captcha_settings_form() {
     return $form;
   }
 
+  // Show a warning about Image CAPTCHA in maintenance mode (on fresh forms).
+  if (variable_get('maintenance_mode', 0) && count($form_state['input']) == 0) {
+    drupal_set_message(
+      t('Your site is operating in maintenance mode, which prevents displaying of CAPTCHA images to anonymous users. As fallback, Image CAPTCHAs will be substituted with Math CAPTCHAs.'),
+      'warning'
+    );
+  }
+
   $form['image_captcha_example'] = array(
     '#type' => 'fieldset',
     '#title' => t('Example'),