diff --git a/federationapi/queue/destinationqueue.go b/federationapi/queue/destinationqueue.go
index 00e02b2d9..768ed1f2b 100644
--- a/federationapi/queue/destinationqueue.go
+++ b/federationapi/queue/destinationqueue.go
@@ -21,16 +21,17 @@ import (
 	"sync"
 	"time"
 
+	"github.com/matrix-org/gomatrix"
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/sirupsen/logrus"
+	"go.uber.org/atomic"
+
 	fedapi "github.com/matrix-org/dendrite/federationapi/api"
 	"github.com/matrix-org/dendrite/federationapi/statistics"
 	"github.com/matrix-org/dendrite/federationapi/storage"
 	"github.com/matrix-org/dendrite/federationapi/storage/shared"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/setup/process"
-	"github.com/matrix-org/gomatrix"
-	"github.com/matrix-org/gomatrixserverlib"
-	"github.com/sirupsen/logrus"
-	"go.uber.org/atomic"
 )
 
 const (
@@ -541,6 +542,8 @@ func (oq *destinationQueue) handleTransactionSuccess(pduCount int, eduCount int)
 	// the pending events and EDUs, and wipe our transaction ID.
 	oq.statistics.Success()
 	oq.pendingMutex.Lock()
+	defer oq.pendingMutex.Unlock()
+
 	for i := range oq.pendingPDUs[:pduCount] {
 		oq.pendingPDUs[i] = nil
 	}
@@ -549,7 +552,6 @@ func (oq *destinationQueue) handleTransactionSuccess(pduCount int, eduCount int)
 	}
 	oq.pendingPDUs = oq.pendingPDUs[pduCount:]
 	oq.pendingEDUs = oq.pendingEDUs[eduCount:]
-	oq.pendingMutex.Unlock()
 
 	if len(oq.pendingPDUs) > 0 || len(oq.pendingEDUs) > 0 {
 		select {
diff --git a/federationapi/queue/queue_test.go b/federationapi/queue/queue_test.go
index 6da9e6b30..40419b91f 100644
--- a/federationapi/queue/queue_test.go
+++ b/federationapi/queue/queue_test.go
@@ -1004,9 +1004,12 @@ func TestQueueInteractsWithRealDatabasePDUAndEDU(t *testing.T) {
 		err := queues.SendEvent(ev, "localhost", []gomatrixserverlib.ServerName{destination})
 		assert.NoError(t, err)
 
+		// NOTE : The server can be blacklisted before this, so manually inject the event
+		// into the database.
 		edu := mustCreateEDU(t)
-		errEDU := queues.SendEDU(edu, "localhost", []gomatrixserverlib.ServerName{destination})
-		assert.NoError(t, errEDU)
+		ephemeralJSON, _ := json.Marshal(edu)
+		nid, _ := db.StoreJSON(pc.Context(), string(ephemeralJSON))
+		db.AssociateEDUWithDestination(pc.Context(), destination, nid, edu.Type, nil)
 
 		checkBlacklisted := func(log poll.LogT) poll.Result {
 			if fc.txCount.Load() == failuresUntilBlacklist {
diff --git a/sytest-blacklist b/sytest-blacklist
index fe48fb791..14edf398a 100644
--- a/sytest-blacklist
+++ b/sytest-blacklist
@@ -22,10 +22,6 @@ Forgotten room messages cannot be paginated
 
 Local device key changes get to remote servers with correct prev_id
 
-# Flakey
-
-Local device key changes appear in /keys/changes
-
 # we don't support groups
 
 Remove group category