diff --git a/aleksis/apps/lesrooster/models.py b/aleksis/apps/lesrooster/models.py
index 7fb31117072095bfff573ac26fd24cbb211a8a6b..b18d01773f1860931b82f3ea8680f0ca1fba00a2 100644
--- a/aleksis/apps/lesrooster/models.py
+++ b/aleksis/apps/lesrooster/models.py
@@ -480,7 +480,7 @@ class LessonBundle(ExtensibleModel):
         )
 
         lesson_bundle.lessons.set(
-            [Lesson.create_from_course(course, validity_range) for course in course_bundle.courses]
+            [Lesson.create_from_course(course, validity_range) for course in course_bundle.courses.all()]
         )
 
         return lesson_bundle