diff --git a/mod/assignment/lib.php b/mod/assignment/lib.php
index 0fd89b8a7b6..ee8726ccc66 100644
--- a/mod/assignment/lib.php
+++ b/mod/assignment/lib.php
@@ -1752,7 +1752,7 @@ class assignment_base {
 
         $submission = $this->get_submission($userid);
 
-        if ($files = $fs->get_area_files($this->context->id, 'mod_assignment', 'submission', $submission->id, "timemodified", false)) {
+        if (($submission) && $files = $fs->get_area_files($this->context->id, 'mod_assignment', 'submission', $submission->id, "timemodified", false)) {
             require_once($CFG->libdir.'/portfoliolib.php');
             require_once($CFG->dirroot . '/mod/assignment/locallib.php');
             $button = new portfolio_add_button();