diff --git a/aleksis/apps/chronos/managers.py b/aleksis/apps/chronos/managers.py
index ce1670f53f79bd21e71b59eb260603825edf0f57..2ba38ff0711f341a242785bf3e9521f470d6d3d3 100644
--- a/aleksis/apps/chronos/managers.py
+++ b/aleksis/apps/chronos/managers.py
@@ -878,7 +878,7 @@ class LessonEventQuerySet(PolymorphicQuerySet):
 
     def for_participant(self, person: Union[int, Person]) -> "LessonEventQuerySet":
         """Get all lesson events the person participates in (including amends)."""
-        amended = self.filter(Q(amended_by__isnull=False) | Q(groups__members=person)).values_list(
+        amended = self.filter(Q(amended_by__isnull=False) & Q(groups__members=person)).values_list(
             "amended_by__pk", flat=True
         )
         return self.filter(Q(groups__members=person) | Q(pk__in=amended)).distinct()
diff --git a/aleksis/apps/chronos/models.py b/aleksis/apps/chronos/models.py
index 9533ce1b0c83519f4b6d3936235e660f0f706e07..732c95d53a22ecdb3764b4f71bf55a5b3aa6e410 100644
--- a/aleksis/apps/chronos/models.py
+++ b/aleksis/apps/chronos/models.py
@@ -1533,7 +1533,7 @@ class LessonEvent(CalendarEvent):
             .get_objects(request, params)
             .not_instance_of(SupervisionEvent)
             .select_related("subject", "course")
-            .prefetch_related("groups", "teachers", "rooms")
+            .prefetch_related("groups", "teachers", "rooms", "groups__members")
         )
 
         if request and not has_person(request.user):