--- a/captcha.module
+++ b/captcha.module
@@ -165,8 +165,9 @@
       }

       // Get placement in form and insert in form.
-      $captcha_placement = _captcha_get_captcha_placement($form_id, $form);
-      _captcha_insert_captcha_element($form, $captcha_placement, $captcha_element);
+      if ($captcha_placement = _captcha_get_captcha_placement($form_id, $form)) {
+        _captcha_insert_captcha_element($form, $captcha_placement, $captcha_element);
+      }

     }
   }