diff --git a/messaging_test.go b/messaging_test.go
index 1bd57c4..afe9948 100644
--- a/messaging_test.go
+++ b/messaging_test.go
@@ -133,8 +133,14 @@ func TestPublishDedupAndReplay(t *testing.T) {
 	h := newHarness(t)
 	ctx := context.Background()
 	var calls sync.Map
+	// The first delivery is held until the repeated publish has been made:
+	// its dedup key is free again as soon as it is finalized.
+	release := make(chan struct{})
+	unblock := sync.OnceFunc(func() { close(release) })
+	defer unblock()
 	workers := hopper.NewWorkers()
 	hopper.Subscribe(workers, hopper.Subscription{Name: "flaky", Pattern: "allocation.created", MaxAttempts: 1}, func(_ context.Context, msg *hopper.Message[allocationCreated]) error {
+		<-release
 		n, _ := calls.LoadOrStore(msg.ID, new(int))
 		*n.(*int)++
 		if *n.(*int) == 1 {
@@ -155,6 +161,7 @@ func TestPublishDedupAndReplay(t *testing.T) {
 	if len(again.Deliveries) != 1 || !again.Deliveries[0].Duplicate || again.Deliveries[0].Job.ID != first.Deliveries[0].Job.ID {
 		t.Errorf("repeated publish = %+v", again.Deliveries[0])
 	}
+	unblock()
 
 	// The single attempt fails and the delivery is dead-lettered; replay
 	// re-drives it and it succeeds.