diff --git a/internal/rdb/rdb.go b/internal/rdb/rdb.go
index 28cc574..5666be6 100644
--- a/internal/rdb/rdb.go
+++ b/internal/rdb/rdb.go
@@ -50,8 +50,8 @@ func (r *RDB) Ping() error {
 	return r.client.Ping().Err()
 }
 
-// KEYS[1] -> asynq:{qname}:t:<task_id>
-// KEYS[2] -> asynq:{qname}:pending
+// KEYS[1] -> asynq:{<qname>}:t:<task_id>
+// KEYS[2] -> asynq:{<qname>}:pending
 // ARGV[1] -> task message data
 // ARGV[2] -> task ID
 var enqueueCmd = redis.NewScript(`
@@ -75,7 +75,8 @@ func (r *RDB) Enqueue(msg *base.TaskMessage) error {
 }
 
 // KEYS[1] -> unique key
-// KEYS[2] -> asynq:{<qname>}:pending
+// KEYS[2] -> asynq:{<qname>}:t:<taskid>
+// KEYS[3] -> asynq:{<qname>}:pending
 // ARGV[1] -> task ID
 // ARGV[2] -> uniqueness lock TTL
 // ARGV[3] -> task message data
@@ -84,7 +85,8 @@ local ok = redis.call("SET", KEYS[1], ARGV[1], "NX", "EX", ARGV[2])
 if not ok then
   return 0
 end
-redis.call("LPUSH", KEYS[2], ARGV[3])
+redis.call("SET", KEYS[2], ARGV[3])
+redis.call("LPUSH", KEYS[3], ARGV[1])
 return 1
 `)
 
@@ -98,9 +100,9 @@ func (r *RDB) EnqueueUnique(msg *base.TaskMessage, ttl time.Duration) error {
 	if err := r.client.SAdd(base.AllQueues, msg.Queue).Err(); err != nil {
 		return err
 	}
-	res, err := enqueueUniqueCmd.Run(r.client,
-		[]string{msg.UniqueKey, base.PendingKey(msg.Queue)},
-		msg.ID.String(), int(ttl.Seconds()), encoded).Result()
+	keys := []string{msg.UniqueKey, base.TaskKey(msg.Queue, msg.ID.String()), base.PendingKey(msg.Queue)}
+	args := []interface{}{msg.ID.String(), int(ttl.Seconds()), encoded}
+	res, err := enqueueUniqueCmd.Run(r.client, keys, args...).Result()
 	if err != nil {
 		return err
 	}
diff --git a/internal/rdb/rdb_test.go b/internal/rdb/rdb_test.go
index 1e8a396..40b2885 100644
--- a/internal/rdb/rdb_test.go
+++ b/internal/rdb/rdb_test.go
@@ -101,7 +101,7 @@ func TestEnqueueUnique(t *testing.T) {
 	m1 := base.TaskMessage{
 		ID:        uuid.New(),
 		Type:      "email",
-		Payload:   map[string]interface{}{"user_id": 123},
+		Payload:   map[string]interface{}{"user_id": float64(123)},
 		Queue:     base.DefaultQueueName,
 		UniqueKey: base.UniqueKey(base.DefaultQueueName, "email", map[string]interface{}{"user_id": 123}),
 	}
@@ -116,13 +116,26 @@ func TestEnqueueUnique(t *testing.T) {
 	for _, tc := range tests {
 		h.FlushDB(t, r.client) // clean up db before each test case.
 
+		// Enqueue the first message, should succeed.
 		err := r.EnqueueUnique(tc.msg, tc.ttl)
 		if err != nil {
 			t.Errorf("First message: (*RDB).EnqueueUnique(%v, %v) = %v, want nil",
 				tc.msg, tc.ttl, err)
 			continue
 		}
+		gotPending := h.GetPendingMessages(t, r.client, tc.msg.Queue)
+		if len(gotPending) != 1 {
+			t.Errorf("%q has length %d, want 1", base.PendingKey(tc.msg.Queue), len(gotPending))
+			continue
+		}
+		if diff := cmp.Diff(tc.msg, gotPending[0]); diff != "" {
+			t.Errorf("persisted data differed from the original input (-want, +got)\n%s", diff)
+		}
+		if !r.client.SIsMember(base.AllQueues, tc.msg.Queue).Val() {
+			t.Errorf("%q is not a member of SET %q", tc.msg.Queue, base.AllQueues)
+		}
 
+		// Enqueue the second message, should fail.
 		got := r.EnqueueUnique(tc.msg, tc.ttl)
 		if got != ErrDuplicateTask {
 			t.Errorf("Second message: (*RDB).EnqueueUnique(%v, %v) = %v, want %v",
@@ -134,9 +147,6 @@ func TestEnqueueUnique(t *testing.T) {
 			t.Errorf("TTL %q = %v, want %v", tc.msg.UniqueKey, gotTTL, tc.ttl)
 			continue
 		}
-		if !r.client.SIsMember(base.AllQueues, tc.msg.Queue).Val() {
-			t.Errorf("%q is not a member of SET %q", tc.msg.Queue, base.AllQueues)
-		}
 	}
 }