Can't encode RawExt

codec.go

package main

import (
	"fmt"

	"github.com/ugorji/go/codec"
)

var mh = codec.MsgpackHandle{}

func main() {
	mh.SignedInteger = false

	data := []byte{0xd4, 42, 84}
	dec := codec.NewDecoderBytes(data, &mh)

	var dd interface{}

	dec.MustDecode(&dd)
	fmt.Printf("%+v, %T\n", dd, dd)

	out := []byte{}
	enc := codec.NewEncoderBytes(&out, &mh)
	enc.MustEncode(dd)
	fmt.Printf("%x\n", out)
}

result.txt

$ go run codec.go
{Tag:42 Data:[84] Value:<nil>}, codec.RawExt
panic: interface conversion: interface is codec.RawExt, not *codec.RawExt

goroutine 1 [running]:
github.com/ugorji/go/codec.encFnInfo.rawExt(0x927568, 0xc20803be00, 0xc20803bef0, 0x4d0d20, 0xc20803bdd0, 0x59)
	/Users/inada-n/go1.4/src/github.com/ugorji/go/codec/encode.go:275 +0x7e
github.com/ugorji/go/codec.(*Encoder).encodeI(0xc20804cbe0, 0x4d0d20, 0xc20803bdd0, 0x0)
	/Users/inada-n/go1.4/src/github.com/ugorji/go/codec/encode.go:953 +0x1df
github.com/ugorji/go/codec.(*Encoder).encode(0xc20804cbe0, 0x4d0d20, 0xc20803bdd0)
	/Users/inada-n/go1.4/src/github.com/ugorji/go/codec/encode.go:943 +0x340
github.com/ugorji/go/codec.(*Encoder).MustEncode(0xc20804cbe0, 0x4d0d20, 0xc20803bdd0)
	/Users/inada-n/go1.4/src/github.com/ugorji/go/codec/encode.go:844 +0x3c
main.main()
	/Users/inada-n/t/codec.go:24 +0x2d5
exit status 2