diff --git a/lib/gradelib.php b/lib/gradelib.php
index 967340a5723..4b1cf8246d8 100644
--- a/lib/gradelib.php
+++ b/lib/gradelib.php
@@ -1115,8 +1115,9 @@ function grade_recover_history_grades($userid, $courseid) {
  * @return bool true if ok, array of errors if problems found. Grade item id => error message
  */
 function grade_regrade_final_grades($courseid, $userid=null, $updated_item=null, $progress=null) {
-    // This may take a very long time.
+    // This may take a very long time and extra memory.
     \core_php_time_limit::raise();
+    raise_memory_limit(MEMORY_EXTRA);
 
     $course_item = grade_item::fetch_course_item($courseid);