diff --git a/internal/rdb/rdb.go b/internal/rdb/rdb.go
index b792c49..d7a03a5 100644
--- a/internal/rdb/rdb.go
+++ b/internal/rdb/rdb.go
@@ -186,11 +186,8 @@ func (r *RDB) dequeue(qnames ...string) (msgjson string, deadline int64, err err
 // KEYS[1] -> asynq:{<qname>}:in_progress
 // KEYS[2] -> asynq:{<qname>}:deadlines
 // KEYS[3] -> asynq:{<qname>}:processed:<yyyy-mm-dd>
-// KEYS[4] -> unique key
 // ARGV[1] -> base.TaskMessage value
 // ARGV[2] -> stats expiration timestamp
-// ARGV[3] -> task ID
-// Note: LREM count ZERO means "remove all elements equal to val"
 var doneCmd = redis.NewScript(`
 if redis.call("LREM", KEYS[1], 0, ARGV[1]) == 0 then
   return redis.error_reply("NOT FOUND")
@@ -202,7 +199,28 @@ local n = redis.call("INCR", KEYS[3])
 if tonumber(n) == 1 then
 	redis.call("EXPIREAT", KEYS[3], ARGV[2])
 end
-if string.len(KEYS[4]) > 0 and redis.call("GET", KEYS[4]) == ARGV[3] then
+return redis.status_reply("OK")
+`)
+
+// KEYS[1] -> asynq:{<qname>}:in_progress
+// KEYS[2] -> asynq:{<qname>}:deadlines
+// KEYS[3] -> asynq:{<qname>}:processed:<yyyy-mm-dd>
+// KEYS[4] -> unique key
+// ARGV[1] -> base.TaskMessage value
+// ARGV[2] -> stats expiration timestamp
+// ARGV[3] -> task ID
+var doneUniqueCmd = redis.NewScript(`
+if redis.call("LREM", KEYS[1], 0, ARGV[1]) == 0 then
+  return redis.error_reply("NOT FOUND")
+end
+if redis.call("ZREM", KEYS[2], ARGV[1]) == 0 then
+  return redis.error_reply("NOT FOUND")
+end
+local n = redis.call("INCR", KEYS[3])
+if tonumber(n) == 1 then
+	redis.call("EXPIREAT", KEYS[3], ARGV[2])
+end
+if redis.call("GET", KEYS[4]) == ARGV[3] then
   redis.call("DEL", KEYS[4])
 end
 return redis.status_reply("OK")
@@ -217,9 +235,18 @@ func (r *RDB) Done(msg *base.TaskMessage) error {
 	}
 	now := time.Now()
 	expireAt := now.Add(statsTTL)
-	return doneCmd.Run(r.client,
-		[]string{base.InProgressKey(msg.Queue), base.DeadlinesKey(msg.Queue), base.ProcessedKey(msg.Queue, now), msg.UniqueKey},
-		encoded, expireAt.Unix(), msg.ID.String()).Err()
+	keys := []string{
+		base.InProgressKey(msg.Queue),
+		base.DeadlinesKey(msg.Queue),
+		base.ProcessedKey(msg.Queue, now),
+	}
+	args := []interface{}{encoded, expireAt.Unix()}
+	if len(msg.UniqueKey) > 0 {
+		keys = append(keys, msg.UniqueKey)
+		args = append(args, msg.ID.String())
+		return doneUniqueCmd.Run(r.client, keys, args...).Err()
+	}
+	return doneCmd.Run(r.client, keys, args...).Err()
 }
 
 // KEYS[1] -> asynq:{<qname>}:in_progress