diff --git a/grade/report/grader/lib.php b/grade/report/grader/lib.php
index 69b1a008ff4..82535428828 100644
--- a/grade/report/grader/lib.php
+++ b/grade/report/grader/lib.php
@@ -596,7 +596,7 @@ class grade_report_grader extends grade_report {
         foreach ($this->users as $userid => $user) {
             $userrow = new html_table_row();
             $userrow->id = 'fixed_user_'.$userid;
-            $userrow->attributes['class'] = 'r'.$this->rowcount++ . $rowclasses[$this->rowcount % 2];
+            $userrow->attributes['class'] = 'r'.$this->rowcount++.' '.$rowclasses[$this->rowcount % 2];
 
             $usercell = new html_table_cell();
             $usercell->attributes['class'] = 'user';