r.go | 2 +-

diff --git a/r.go b/r.go
index b9e48269ba45d81371c8298caec644a55176685ffce110c7f89197f7b69a8348..aea59999bd02e2df289822e519d7c8d005a66cab165ff7d580c7928171ca297b 100644
--- a/r.go
+++ b/r.go
@@ -48,7 +48,7 @@ 	p, _ := r.r.Peek(21)
 	if len(p) == 0 {
 		return 0, io.EOF
 	}
-	idx := bytes.Index(p, []byte{':'})
+	idx := bytes.IndexByte(p, ':')
 	if idx == -1 {
 		return 0, errors.New("no length separator found")
 	}