diff --git a/federationsender/queue/destinationqueue.go b/federationsender/queue/destinationqueue.go
index accd39f4d..1d159b9c2 100644
--- a/federationsender/queue/destinationqueue.go
+++ b/federationsender/queue/destinationqueue.go
@@ -225,7 +225,7 @@ func (oq *destinationQueue) backgroundSend() {
 		}
 
 		// If we have pending PDUs or EDUs then construct a transaction.
-		for oq.pendingPDUs.Load() > 0 || len(oq.pendingEDUs) > 0 {
+		if oq.pendingPDUs.Load() > 0 || len(oq.pendingEDUs) > 0 {
 			// Try sending the next transaction and see what happens.
 			transaction, terr := oq.nextTransaction(oq.pendingEDUs)
 			if terr != nil {
@@ -275,6 +275,17 @@ func (oq *destinationQueue) backgroundSend() {
 				oq.cleanPendingInvites()
 			}
 		}
+
+		// If something else has come along since we sent the previous
+		// transactions then we want the next loop iteration to skip the
+		// wait and not go to sleep. In which case, if there isn't a
+		// wake-up message already, send one.
+		if oq.pendingPDUs.Load() > 0 {
+			select {
+			case oq.notifyPDUs <- true:
+			default:
+			}
+		}
 	}
 }
 
diff --git a/federationsender/queue/queue.go b/federationsender/queue/queue.go
index 6c7fca54e..2288689ee 100644
--- a/federationsender/queue/queue.go
+++ b/federationsender/queue/queue.go
@@ -93,7 +93,7 @@ func (oqs *OutgoingQueues) getQueue(destination gomatrixserverlib.ServerName) *d
 			statistics:       oqs.statistics.ForServer(destination),
 			incomingEDUs:     make(chan *gomatrixserverlib.EDU, 128),
 			incomingInvites:  make(chan *gomatrixserverlib.InviteV2Request, 128),
-			notifyPDUs:       make(chan bool, 128),
+			notifyPDUs:       make(chan bool, 1),
 			interruptBackoff: make(chan bool),
 			signing:          oqs.signing,
 		}