diff --git a/roomserver/internal/api.go b/roomserver/internal/api.go
index 5cfe68daa..e370f7e44 100644
--- a/roomserver/internal/api.go
+++ b/roomserver/internal/api.go
@@ -72,9 +72,6 @@ func NewRoomserverAPI(
 		},
 		// perform-er structs get initialised when we have a federation sender to use
 	}
-	if err := a.Inputer.Start(); err != nil {
-		logrus.WithError(err).Panic("failed to start roomserver input API")
-	}
 	return a
 }
 
@@ -140,6 +137,10 @@ func (r *RoomserverInternalAPI) SetFederationAPI(fsAPI fsAPI.FederationInternalA
 	r.Forgetter = &perform.Forgetter{
 		DB: r.DB,
 	}
+
+	if err := r.Inputer.Start(); err != nil {
+		logrus.WithError(err).Panic("failed to start roomserver input API")
+	}
 }
 
 func (r *RoomserverInternalAPI) SetAppserviceAPI(asAPI asAPI.AppServiceQueryAPI) {
diff --git a/roomserver/internal/input/input.go b/roomserver/internal/input/input.go
index 1eab67802..dbff5fdda 100644
--- a/roomserver/internal/input/input.go
+++ b/roomserver/internal/input/input.go
@@ -59,14 +59,15 @@ func (r *Inputer) Start() error {
 		// later, possibly with an error response to the inputter if synchronous.
 		func(msg *nats.Msg) {
 			roomID := msg.Header.Get("room_id")
-			defer roomserverInputBackpressure.With(prometheus.Labels{"room_id": roomID}).Dec()
 			var inputRoomEvent api.InputRoomEvent
 			if err := json.Unmarshal(msg.Data, &inputRoomEvent); err != nil {
 				_ = msg.Term()
 				return
 			}
 			inbox, _ := r.workers.LoadOrStore(roomID, &phony.Inbox{})
+			roomserverInputBackpressure.With(prometheus.Labels{"room_id": roomID}).Inc()
 			inbox.(*phony.Inbox).Act(nil, func() {
+				defer roomserverInputBackpressure.With(prometheus.Labels{"room_id": roomID}).Dec()
 				if err := r.processRoomEvent(context.TODO(), &inputRoomEvent); err != nil {
 					sentry.CaptureException(err)
 				} else {
@@ -111,15 +112,17 @@ func (r *Inputer) InputRoomEvents(
 			if _, err = r.JetStream.PublishMsg(msg); err != nil {
 				return
 			}
-			roomserverInputBackpressure.With(prometheus.Labels{"room_id": roomID}).Inc()
 		}
 	} else {
 		responses := make(chan error, len(request.InputRoomEvents))
 		defer close(responses)
 		for _, e := range request.InputRoomEvents {
 			inputRoomEvent := e
-			inbox, _ := r.workers.LoadOrStore(inputRoomEvent.Event.RoomID(), &phony.Inbox{})
+			roomID := inputRoomEvent.Event.RoomID()
+			inbox, _ := r.workers.LoadOrStore(roomID, &phony.Inbox{})
+			roomserverInputBackpressure.With(prometheus.Labels{"room_id": roomID}).Inc()
 			inbox.(*phony.Inbox).Act(nil, func() {
+				defer roomserverInputBackpressure.With(prometheus.Labels{"room_id": roomID}).Dec()
 				err := r.processRoomEvent(context.TODO(), &inputRoomEvent)
 				if err != nil {
 					sentry.CaptureException(err)