diff --git a/roomserver/api/wrapper.go b/roomserver/api/wrapper.go
index 82a4a5719..2e0e0273f 100644
--- a/roomserver/api/wrapper.go
+++ b/roomserver/api/wrapper.go
@@ -42,10 +42,11 @@ func SendEvents(
 
 // SendEventWithState writes an event with KindNew to the roomserver
 // with the state at the event as KindOutlier before it. Will not send any event that is
-// marked as `true` in haveEventIDs
+// marked as `true` in haveEventIDs.  The event itself is optional in case
+// hou just want to write outliers to the roomserver.
 func SendEventWithState(
 	ctx context.Context, rsAPI RoomserverInternalAPI, state *gomatrixserverlib.RespState,
-	event gomatrixserverlib.HeaderedEvent, haveEventIDs map[string]bool,
+	event *gomatrixserverlib.HeaderedEvent, haveEventIDs map[string]bool,
 ) error {
 	outliers, err := state.Events()
 	if err != nil {
@@ -69,13 +70,15 @@ func SendEventWithState(
 		stateEventIDs[i] = state.StateEvents[i].EventID()
 	}
 
-	ires = append(ires, InputRoomEvent{
-		Kind:          KindNew,
-		Event:         event,
-		AuthEventIDs:  event.AuthEventIDs(),
-		HasState:      true,
-		StateEventIDs: stateEventIDs,
-	})
+	if event != nil {
+		ires = append(ires, InputRoomEvent{
+			Kind:          KindNew,
+			Event:         *event,
+			AuthEventIDs:  event.AuthEventIDs(),
+			HasState:      true,
+			StateEventIDs: stateEventIDs,
+		})
+	}
 
 	return SendInputRoomEvents(ctx, rsAPI, ires)
 }