--- assignment.class.php.orig	2011-03-17 18:56:38.000000000 +0100
+++ assignment.class.php	2011-03-17 19:04:03.000000000 +0100
@@ -28,7 +28,7 @@
         if (!has_capability('mod/assignment:submit', $context)) {
             $editable = null;
         } else {
-            $editable = $this->isopen() && (!$submission || $this->assignment->resubmit || !$submission->timemarked);
+            $editable = $this->isopen() && (!$submission || $this->assignment->resubmit || ($submission->grade < 0));
         }
         $editmode = ($editable and $edit);