diff --git a/grade/lib.php b/grade/lib.php
index 8c4d100084c..f3b637d71fa 100644
--- a/grade/lib.php
+++ b/grade/lib.php
@@ -2379,7 +2379,10 @@ class grade_structure {
                 ['id' => $this->courseid, 'sesskey' => sesskey(), 'eid' => $element['eid']]);
             $url = $gpr->add_url_params($url);
 
-            if (($element['type'] == 'grade') && ($element['object']->grade_item->is_locked())) {
+            if ($element['type'] == 'category') {
+                // Grade categories themselves cannot be locked.
+                return null;
+            } else if (($element['type'] == 'grade') && ($element['object']->grade_item->is_locked())) {
                 // Don't allow an unlocking action for a grade whose grade item is locked: just print a state icon.
                 $strparamobj = new stdClass();
                 $strparamobj->itemname = $element['object']->grade_item->get_name(true, true);
@@ -2520,6 +2523,7 @@ class grade_structure {
 
         if (isset($element['type']) && ($element['type'] == 'category')) {
             $context['classes'] = 'category_grade_icons';
+            $context['locked'] = false;
         }
 
         return $OUTPUT->render_from_template('core_grades/status_icons', $context);
@@ -2651,7 +2655,6 @@ class grade_structure {
                     }
                     $context->editurl = $this->get_edit_link($element, $gpr);
                     $context->hideurl = $this->get_hiding_link($element, $gpr);
-                    $context->lockurl = $this->get_locking_link($element, $gpr);
                 }
             }