diff --git a/common/redisclient.go b/common/redisclient.go
index 2758ff8..d792cc1 100644
--- a/common/redisclient.go
+++ b/common/redisclient.go
@@ -6,10 +6,13 @@ package common
 
 import (
 	"bufio"
+	"bytes"
+	"errors"
 	"fmt"
 	"net"
 	"strconv"
 	"sync"
+	"unicode"
 )
 
 type RedisClient struct {
@@ -106,6 +109,16 @@ func isError(line []byte) error {
 	return nil
 }
 
+// parseSize is a cheaper replacement for fmt.Sscanf(string(line), "$%d\r\n", &size).
+func parseSize(line []byte) (int, error) {
+	if len(line) < 1 || line[0] != '$' {
+		return 0, errors.New("Missing '$' at begin of line")
+	}
+	line = bytes.TrimFunc(line[1:], unicode.IsSpace)
+	v, err := strconv.ParseInt(string(line), 10, 0)
+	return int(v), err
+}
+
 func (client *RedisClient) readBulkString(data *[]byte) (size int, err error) {
 	var line []byte
 	if line, err = client.reader.ReadBytes('\n'); err != nil {
@@ -114,10 +127,7 @@ func (client *RedisClient) readBulkString(data *[]byte) (size int, err error) {
 	if err = isError(line); err != nil {
 		return
 	}
-	if _, err = fmt.Sscanf(string(line), "$%d\r\n", &size); err != nil {
-		return
-	}
-	if size <= 0 {
+	if size, err = parseSize(line); err != nil || size <= 0 {
 		return
 	}
 	if cap(*data) < size {
@@ -158,7 +168,7 @@ func (client *RedisClient) QueryCuboid(cuboid Cuboid, fn func(*Block)) (err erro
 			return
 		}
 		block.Coord = PlainToCoord(key)
-		if size, err = client.readBulkString(&data); err != nil {
+		if size, err = client.readBulkString(&data); err != nil || size < 0 {
 			return
 		}
 		block.Data = data[0:size]