diff --git a/grade/edit/tree/index.php b/grade/edit/tree/index.php
index 2285c6baba9..831364f3f18 100644
--- a/grade/edit/tree/index.php
+++ b/grade/edit/tree/index.php
@@ -316,7 +316,9 @@ echo '<input type="hidden" name="sesskey" value="'.sesskey().'" />';
 
 // Build up an array of categories for move drop-down (by reference)
 $categories = array();
-echo $grade_edit_tree->build_html_tree($gtree->top_element, true, array(), $categories);
+$level     = 0;
+$row_count = 0;
+echo $grade_edit_tree->build_html_tree($gtree->top_element, true, array(), $categories, $level, $row_count);
 
 echo '<div id="gradetreesubmit">';
 if (!$moving) {
diff --git a/grade/edit/tree/lib.php b/grade/edit/tree/lib.php
index 531c872c50b..7ebdd820237 100755
--- a/grade/edit/tree/lib.php
+++ b/grade/edit/tree/lib.php
@@ -88,7 +88,7 @@ class grade_edit_tree {
      *
      * @return string HTML
      */
-    function build_html_tree($element, $totals, $parents=array(), &$categories=array(), $level=0, &$row_count=0) {
+    function build_html_tree($element, $totals, $parents, &$categories, $level, &$row_count) {
         global $CFG, $COURSE, $USER;
 
         $object = $element['object'];