diff --git a/question/type/datasetdependent/abstractqtype.php b/question/type/datasetdependent/abstractqtype.php
index a4ef6942252..75505e9a749 100644
--- a/question/type/datasetdependent/abstractqtype.php
+++ b/question/type/datasetdependent/abstractqtype.php
@@ -79,6 +79,9 @@ class question_dataset_dependent_questiontype extends default_questiontype {
 
     function substitute_variables($str, $dataset) {
         foreach ($dataset as $name => $value) {
+            if($value < 0 ){
+                $str = str_replace('{'.$name.'}', '('.$value.')', $str);
+            } else {
             $str = str_replace('{'.$name.'}', $value, $str);
         }
         return $str;