diff --git a/grade/report/grader/lib.php b/grade/report/grader/lib.php
index 89b7624b93c..b8e99e75293 100644
--- a/grade/report/grader/lib.php
+++ b/grade/report/grader/lib.php
@@ -613,12 +613,12 @@ class grade_report_grader extends grade_report {
         $numusers      = count($this->users);
 
         // Preload scale objects for items with a scaleid
-        $scales_list = '';
+        $scales_list = array();
         $tabindices = array();
 
         foreach ($this->gtree->get_items() as $item) {
             if (!empty($item->scaleid)) {
-                $scales_list .= "$item->scaleid,";
+                $scales_list[] = $item->scaleid;
             }
 
             $tabindices[$item->id]['grade'] = $gradetabindex;
@@ -628,7 +628,6 @@ class grade_report_grader extends grade_report {
         $scales_array = array();
 
         if (!empty($scales_list)) {
-            $scales_list = substr($scales_list, 0, -1);
             $scales_array = $DB->get_records_list('scale', 'id', $scales_list);
         }