r.go | 14 +++-----------

diff --git a/r.go b/r.go
index 4833688cf6e9f7c230291fe3df9fa59a3ec353313e27272a29e958d0b3b24d4b..6789d4fc89f7b6e28e1835a9c135329a6765ad4f91eb1e6147d2c1b53bd3e9d2 100644
--- a/r.go
+++ b/r.go
@@ -19,7 +19,6 @@ package netstring
 
 import (
 	"bufio"
-	"bytes"
 	"errors"
 	"io"
 	"strconv"
@@ -44,19 +43,12 @@ func (r *Reader) Next() (uint64, error) {
 	if !r.eof {
 		return 0, errors.New("current chunk is unread")
 	}
-	p, _ := r.r.Peek(21)
-	if len(p) == 0 {
-		return 0, io.EOF
-	}
-	idx := bytes.IndexByte(p, ':')
-	if idx == -1 {
-		return 0, errors.New("no length separator found")
-	}
-	size, err := strconv.ParseUint(string(p[:idx]), 10, 64)
+	lenRaw, err := r.r.ReadSlice(':')
 	if err != nil {
 		return 0, err
 	}
-	if _, err = r.r.Discard(idx + 1); err != nil {
+	size, err := strconv.ParseUint(string(lenRaw[:len(lenRaw)-1]), 10, 64)
+	if err != nil {
 		return 0, err
 	}
 	r.left = size