diff --git a/mod/forum/lib.php b/mod/forum/lib.php
index eb6ebb0d434..85231d54036 100644
--- a/mod/forum/lib.php
+++ b/mod/forum/lib.php
@@ -6941,7 +6941,7 @@ class forum_portfolio_caller extends portfolio_module_caller_base {
 
     function get_return_url() {
         global $CFG;
-        return $CFG->wwwroot . '/mod/forum/discuss.php?d=' . $this->cm->id;
+        return $CFG->wwwroot . '/mod/forum/discuss.php?d=' . $this->discussion->id;
     }
 
     function get_navigation() {