diff --git a/grade/report/grader/lib.php b/grade/report/grader/lib.php
index 21bb72a64d0..0ea6cf737b8 100644
--- a/grade/report/grader/lib.php
+++ b/grade/report/grader/lib.php
@@ -863,7 +863,7 @@ class grade_report_grader extends grade_report {
             foreach ($this->items as $item) {
                 // If the user shouldn't see this grade_item, hide the average as well
                 // MDL-11576 If any of the grades are hidden and the user doesn't have permission to view them, hide average as well
-                if (($item->is_hidden() || $item->has_hidden_grades()) && !$canviewhidden) {
+                if (($item->is_hidden() || $item->has_hidden_grades($groupsql, $groupwheresql)) && !$canviewhidden) {
                     $avghtml .= '<td class="cell c' . $columncount++.'"> - </td>';
                     continue;
                 }
diff --git a/lib/grade/grade_item.php b/lib/grade/grade_item.php
index a6387b29bd2..7dcea7a033f 100644
--- a/lib/grade/grade_item.php
+++ b/lib/grade/grade_item.php
@@ -569,8 +569,10 @@ class grade_item extends grade_object {
      * Returns the number of grades that are hidden.
      * @param return int Number of hidden grades
      */
-    function has_hidden_grades() {
-        return count_records('grade_grades', 'itemid', $this->id, 'hidden', 1);
+    function has_hidden_grades($groupsql = null, $groupwheresql = null) {
+        global $CFG;
+        return get_field_sql("SELECT COUNT(*) FROM {$CFG->prefix}grade_grades g LEFT JOIN "
+                            ."{$CFG->prefix}user u ON g.userid = u.id$groupsql WHERE itemid = $this->id AND hidden = 1 $groupwheresql");
     }
 
     /**