diff --git a/includes/smarty.php b/includes/smarty.php
index 5b8fdb4..17ce792 100644
--- a/includes/smarty.php
+++ b/includes/smarty.php
@@ -150,6 +150,10 @@ function display_ajax_return($data=null, $pretty=false) {
   global $debug_ajax;
   if (is_null($data))
     $data = array();
+  // Adjust HTTP error code on unsuccessfull request
+  elseif (isset($data['success']) && !$data['success'] && http_response_code() == 200)
+    http_response_code(400);
+
   if (isset($_SESSION['messages']) && !empty($_SESSION['messages'])) {
     $data['messages'] = $_SESSION['messages'];
     unset($_SESSION['messages']);