unmarshal [] into a slice makes the slice nil, not empty

code:
package main

import "launchpad.net/goyaml"
import "fmt"

func main() {
 s := []string{}
 data, _ := goyaml.Marshal(s)
 fmt.Printf("%s\n", string(data))
 var s2 []string
 goyaml.Unmarshal(data, &s2)
 fmt.Printf("%#v\n", s2)
}

output:
[]

[]string(nil)

expected output:
[]

[]string{}