diff --git a/mod/assignment/lib.php b/mod/assignment/lib.php
index 9ef8e662356..8150c42b509 100644
--- a/mod/assignment/lib.php
+++ b/mod/assignment/lib.php
@@ -385,10 +385,10 @@ class assignment_base {
         // will create a new instance and return the id number
         // of the new instance.
 
-        $assignment->timemodified = time();
         $assignment->timemodified = time();
         if (empty($assignment->dueenable)) {
             $assignment->timedue = 0;
+            $assignment->preventlate = 0;
         } else {
             $assignment->timedue = make_timestamp($assignment->dueyear, $assignment->duemonth, 
                                                   $assignment->dueday, $assignment->duehour, 
@@ -396,7 +396,6 @@ class assignment_base {
         }
         if (empty($assignment->availableenable)) {
             $assignment->timeavailable = 0;
-            $assignment->preventlate = 0;
         } else {
             $assignment->timeavailable = make_timestamp($assignment->availableyear, $assignment->availablemonth, 
                                                         $assignment->availableday, $assignment->availablehour,