diff --git a/pub/fed_test.go b/pub/fed_test.go
index 422050b..f743925 100644
--- a/pub/fed_test.go
+++ b/pub/fed_test.go
@@ -2172,10 +2172,13 @@ func TestPostInbox_Create_SetsObject(t *testing.T) {
 	req := ActivityPubRequest(httptest.NewRequest("POST", testInboxURI, bytes.NewBuffer(MustSerialize(testCreateNote))))
 	gotSet := 0
 	var setObject PubObject
+	var gotSetInbox PubObject
 	app.MockFederateApp.set = func(c context.Context, o PubObject) error {
 		gotSet++
 		if gotSet == 1 {
 			setObject = o
+		} else if gotSet == 2 {
+			gotSetInbox = o
 		}
 		return nil
 	}
@@ -2183,6 +2186,9 @@ func TestPostInbox_Create_SetsObject(t *testing.T) {
 		return nil
 	}
 	handled, err := p.PostInbox(context.Background(), resp, req)
+	expectedInbox := &vocab.OrderedCollection{}
+	expectedInbox.AppendType("OrderedCollection")
+	expectedInbox.AppendOrderedItemsIRI(testCreateNote.GetId())
 	if err != nil {
 		t.Fatal(err)
 	} else if !handled {
@@ -2191,6 +2197,8 @@ func TestPostInbox_Create_SetsObject(t *testing.T) {
 		t.Fatalf("expected %d, got %d", 2, gotSet)
 	} else if err := PubObjectEquals(setObject, testNote); err != nil {
 		t.Fatalf("unexpected set object: %s", err)
+	} else if err := PubObjectEquals(gotSetInbox, expectedInbox); err != nil {
+		t.Fatalf("unexpected callback object: %s", err)
 	}
 }
 
@@ -4497,7 +4505,7 @@ func TestPostOutbox_Create_SetCreatedObject(t *testing.T) {
 	handled, err := p.PostOutbox(context.Background(), resp, req)
 	expectedOutbox := &vocab.OrderedCollection{}
 	expectedOutbox.AppendType("OrderedCollection")
-	expectedOutbox.AppendOrderedItemsObject(testClientExpectedCreateNote)
+	expectedOutbox.AppendOrderedItemsIRI(testClientExpectedCreateNote.GetId())
 	if err != nil {
 		t.Fatal(err)
 	} else if !handled {
diff --git a/pub/internal.go b/pub/internal.go
index 0bb260d..9ee1da5 100644
--- a/pub/internal.go
+++ b/pub/internal.go
@@ -1726,7 +1726,6 @@ func (f *federator) ownsAnyObjects(c context.Context, a vocab.ActivityType) (boo
 	return f.ownsAnyIRIs(c, iris), nil
 }
 
-// TODO: Only Set IRIs
 func (f *federator) addToOutbox(c context.Context, r *http.Request, m map[string]interface{}) error {
 	outbox, err := f.App.GetOutbox(c, r, ReadWrite)
 	if err != nil {
@@ -1739,11 +1738,13 @@ func (f *federator) addToOutbox(c context.Context, r *http.Request, m map[string
 	if err := f.App.Set(c, activity); err != nil {
 		return err
 	}
-	outbox.PrependOrderedItemsObject(activity)
+	if !activity.HasId() {
+		return fmt.Errorf("activity missing id")
+	}
+	outbox.PrependOrderedItemsIRI(activity.GetId())
 	return f.App.Set(c, outbox)
 }
 
-// TODO: Only Set IRIs
 func (f *federator) addToInbox(c context.Context, r *http.Request, m map[string]interface{}) error {
 	inbox, err := f.App.GetInbox(c, r, ReadWrite)
 	if err != nil {
@@ -1757,8 +1758,11 @@ func (f *federator) addToInbox(c context.Context, r *http.Request, m map[string]
 	if err != nil {
 		return err
 	}
+	if !activity.HasId() {
+		return fmt.Errorf("activity missing id")
+	}
 	if !iriSet[activity.GetId().String()] {
-		inbox.PrependOrderedItemsObject(activity)
+		inbox.PrependOrderedItemsIRI(activity.GetId())
 		return f.App.Set(c, inbox)
 	}
 	return nil