diff --git a/classes/studyplan.php b/classes/studyplan.php
index 0caed9c..7deb8fd 100644
--- a/classes/studyplan.php
+++ b/classes/studyplan.php
@@ -636,7 +636,8 @@ class studyplan {
 
         $sql = "SELECT i.course_id
                 FROM {local_treestudyplan} p
-                INNER JOIN {local_treestudyplan_line} l ON p.id = l.studyplan_id
+                INNER JOIN {local_treestudyplan_page} pg ON p.id = pg.studyplan_id
+                INNER JOIN {local_treestudyplan_line} l ON pg.id = l.page_id
                 INNER JOIN {local_treestudyplan_item} i ON l.id = i.line_id
                 WHERE p.id = :studyplan_id AND i.type = :itemtype";
         $fields = $DB->get_fieldset_sql($sql,["studyplan_id" => $this->id,"itemtype" => studyitem::COURSE]);