diff --git a/program/lib/Roundcube/rcube_output.php b/program/lib/Roundcube/rcube_output.php
index 42e2b756444..359128d540b 100644
--- a/program/lib/Roundcube/rcube_output.php
+++ b/program/lib/Roundcube/rcube_output.php
@@ -327,7 +327,7 @@ public static function get_edit_field($col, $value, $attrib, $type = 'text')
     public static function json_serialize($input, $pretty = false)
     {
         $input   = rcube_charset::clean($input);
-        $options = 0;
+        $options = JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE;
 
         if ($pretty) {
             $options |= JSON_PRETTY_PRINT;