diff --git a/mod/workshop/db/upgrade.php b/mod/workshop/db/upgrade.php
index 60bba12..a6ed7fc 100644
--- a/mod/workshop/db/upgrade.php
+++ b/mod/workshop/db/upgrade.php
@@ -147,7 +147,8 @@ function xmldb_workshop_upgrade($oldversion) {
             upgrade_set_timeout(60); // set up timeout, may also abort execution
             $pbar->update($i, $count, "Migrating workshop submissions - $i/$count");
 
-            $filedir = "$CFG->dataroot/$submission->course/$CFG->moddata/workshop/$submission->id";
+            $wso = $DB->get_record('workshop_submissions_old', array('newid' => $submission->id));
+            $filedir = "$CFG->dataroot/$submission->course/$CFG->moddata/workshop/$wso->id";
             if ($files = get_directory_list($filedir, '', false)) {
                 $context = get_context_instance(CONTEXT_MODULE, $submission->cmid);
                 foreach ($files as $filename) {
@@ -178,7 +179,7 @@ function xmldb_workshop_upgrade($oldversion) {
                 }
             }
             // remove dirs if empty
-            @rmdir("$CFG->dataroot/$submission->course/$CFG->moddata/workshop/$submission->id");
+            @rmdir("$CFG->dataroot/$submission->course/$CFG->moddata/workshop/$wso->id");
             @rmdir("$CFG->dataroot/$submission->course/$CFG->moddata/workshop");
             @rmdir("$CFG->dataroot/$submission->course/$CFG->moddata");
             @rmdir("$CFG->dataroot/$submission->course");