diff --git a/docroot/sites/all/modules/contrib/captcha/captcha.module b/docroot/sites/all/modules/contrib/captcha/captcha.module
index 1a304ae0..7dd0fc48 100644
--- a/docroot/sites/all/modules/contrib/captcha/captcha.module
+++ b/docroot/sites/all/modules/contrib/captcha/captcha.module
@@ -631,7 +631,7 @@ function _captcha_get_posted_captcha_info($element, $form_state, $this_form_id)
       $posted_form_id = isset($form_state['input']['form_id']) ? $form_state['input']['form_id'] : '';
     }
 
-    $posted_captcha_sid = isset($form_state['captcha_info']['captcha_sid']) ? $form_state['captcha_info']['captcha_sid'] : '';
+    $posted_captcha_sid = isset($form_state['captcha_info']['captcha_sid']) ? $form_state['captcha_info']['captcha_sid'] : NULL;
   }
   else if ($form_state['submitted'] && isset($form_state['captcha_info'])) {
     // We are handling (or rebuilding) an already submitted form,