diff --git a/mod/quiz/lib.php b/mod/quiz/lib.php
index 9a5abcefe79..e09824cc416 100644
--- a/mod/quiz/lib.php
+++ b/mod/quiz/lib.php
@@ -376,6 +376,26 @@ function quiz_grade_item_update($quiz, $grades=NULL) {
         $params['reset'] = true;
         $grades = NULL;
     }
+    
+    $gradebook_grades = grade_get_grades($quiz->course, 'mod', 'quiz', $quiz->id);
+    $grade_item = $gradebook_grades->items[0];
+    if ($grade_item->locked) {
+        $confirm_regrade = optional_param('confirm_regrade', 0, PARAM_INT);
+        if (!$confirm_regrade) {
+            $message = get_string('gradeitemislocked', 'grades');
+            $back_link = $CFG->wwwroot . '/mod/quiz/report.php?q=' . $quiz->id . '&mode=overview';
+            $regrade_link = qualified_me() . '&confirm_regrade=1';
+            print_box_start('generalbox', 'notice');
+            echo '<p>'. $message .'</p>';
+            echo '<div class="buttons">';
+            print_single_button($regrade_link, null, get_string('regradeanyway', 'grades'), 'post', $CFG->framename);
+            print_single_button($back_link,  null,  get_string('cancel'),  'post',  $CFG->framename);
+            echo '</div>';
+            print_box_end();
+
+            return GRADE_UPDATE_ITEM_LOCKED;
+        }
+    }
 
     return grade_update('mod/quiz', $quiz->course, 'mod', 'quiz', $quiz->id, 0, $grades, $params);
 }