diff --git a/src/api/invitations.py b/src/api/invitations.py
index 861f5a4..d09bdf4 100644
--- a/src/api/invitations.py
+++ b/src/api/invitations.py
@@ -120,7 +120,7 @@ class InvitationCreateData(_BaseInvitationData):
                 user=invitee,
                 event_type="invitation",
                 message="new-invitation",
-                data=invitation.id,
+                data=str(cast(PydanticObjectId, invitation.id)),
                 read=False,
             )
             notification = await notification.create()
@@ -232,7 +232,7 @@ async def accept_invitation(invitation_id: PydanticObjectId, user: CurrentUserDe
         user=invitation.invitor,
         event_type="invitation",
         message="invitation-accepted",
-        data=invitation.id,
+        data=str(cast(PydanticObjectId, invitation.id)),
         read=False,
     )
     notification = await notification.create()
@@ -265,7 +265,7 @@ async def decline_invitation(invitation_id: PydanticObjectId, user: CurrentUserD
         user=invitation.invitor,
         event_type="invitation",
         message="invitation-declined",
-        data=invitation.id,
+        data=str(cast(PydanticObjectId, invitation.id)),
         read=False,
     )
     notification = await notification.create()