diff --git a/src/core/models/events.py b/src/core/models/events.py
index 3d458d1bdfc12cb7a4576e94f33a4c14fde0ac71..36c12777f231b00f3ce52084ecea37bfb37da595 100644
--- a/src/core/models/events.py
+++ b/src/core/models/events.py
@@ -182,7 +182,7 @@ class Event(TaggedItemMixin, BackendMixin, ActivityLogMixin, models.Model):
         persons = [participant.participant for participant in self.participants.filter(is_public=True, role=EventParticipant.Role.SPEAKER)]
 
         if len(persons) == 0 and self.kind == Event.Kind.SELF_ORGANIZED and self.owner:
-            persons.add(self.owner)
+            persons.append(self.owner)
 
         return persons