diff --git a/src/github.com/matrix-org/dendrite/federationsender/queue/destinationqueue.go b/src/github.com/matrix-org/dendrite/federationsender/queue/destinationqueue.go
index c1bce8efc..ac243b502 100644
--- a/src/github.com/matrix-org/dendrite/federationsender/queue/destinationqueue.go
+++ b/src/github.com/matrix-org/dendrite/federationsender/queue/destinationqueue.go
@@ -28,7 +28,7 @@ import (
 // ensures that only one request is in flight to a given destination
 // at a time.
 type destinationQueue struct {
-	mutex              sync.Mutex
+	runningMutex       sync.Mutex
 	client             *gomatrixserverlib.FederationClient
 	origin             gomatrixserverlib.ServerName
 	destination        gomatrixserverlib.ServerName
@@ -42,10 +42,11 @@ type destinationQueue struct {
 // If the queue is empty then it starts a background goroutine to
 // start sending events to that destination.
 func (oq *destinationQueue) sendEvent(ev *gomatrixserverlib.Event) {
-	oq.mutex.Lock()
-	defer oq.mutex.Unlock()
+	oq.runningMutex.Lock()
+	defer oq.runningMutex.Unlock()
 	oq.pendingEvents = append(oq.pendingEvents, ev)
 	if !oq.running {
+		oq.running = true
 		go oq.backgroundSend()
 	}
 }
@@ -76,8 +77,8 @@ func (oq *destinationQueue) backgroundSend() {
 // and flushes the queue.
 // Returns nil if the queue was empty.
 func (oq *destinationQueue) next() *gomatrixserverlib.Transaction {
-	oq.mutex.Lock()
-	defer oq.mutex.Unlock()
+	oq.runningMutex.Lock()
+	defer oq.runningMutex.Unlock()
 	if len(oq.pendingEvents) == 0 {
 		oq.running = false
 		return nil
diff --git a/src/github.com/matrix-org/dendrite/federationsender/queue/queue.go b/src/github.com/matrix-org/dendrite/federationsender/queue/queue.go
index 52692d92d..77b245630 100644
--- a/src/github.com/matrix-org/dendrite/federationsender/queue/queue.go
+++ b/src/github.com/matrix-org/dendrite/federationsender/queue/queue.go
@@ -25,10 +25,10 @@ import (
 // OutgoingQueues is a collection of queues for sending transactions to other
 // matrix servers
 type OutgoingQueues struct {
-	mutex  sync.Mutex
-	queues map[gomatrixserverlib.ServerName]*destinationQueue
-	origin gomatrixserverlib.ServerName
-	client *gomatrixserverlib.FederationClient
+	origin      gomatrixserverlib.ServerName
+	client      *gomatrixserverlib.FederationClient
+	queuesMutex sync.Mutex
+	queues      map[gomatrixserverlib.ServerName]*destinationQueue
 }
 
 // NewOutgoingQueues makes a new OutgoingQueues
@@ -63,8 +63,8 @@ func (oqs *OutgoingQueues) SendEvent(
 		"destinations": destinations, "event": ev.EventID(),
 	}).Info("Sending event")
 
-	oqs.mutex.Lock()
-	defer oqs.mutex.Unlock()
+	oqs.queuesMutex.Lock()
+	defer oqs.queuesMutex.Unlock()
 	for _, destination := range destinations {
 		oq := oqs.queues[destination]
 		if oq == nil {
diff --git a/src/github.com/matrix-org/dendrite/federationsender/storage/storage.go b/src/github.com/matrix-org/dendrite/federationsender/storage/storage.go
index ca820b195..2f98093e4 100644
--- a/src/github.com/matrix-org/dendrite/federationsender/storage/storage.go
+++ b/src/github.com/matrix-org/dendrite/federationsender/storage/storage.go
@@ -70,7 +70,8 @@ func (d *Database) SetPartitionOffset(topic string, partition int32, offset int6
 	return d.UpsertPartitionOffset(topic, partition, offset)
 }
 
-// UpdateRoom updates the joined hosts for a room.
+// UpdateRoom updates the joined hosts for a room and returns what the joined
+// hosts were before the update.
 func (d *Database) UpdateRoom(
 	roomID, oldEventID, newEventID string,
 	addHosts []types.JoinedHost,