Deserialisation error of Serialised enum with struct

[misos1]

Here deserialisation is returning Syntax("invalid value: integer 10, expected field index 0 <= i < 1"):

#[derive(Serialize, Deserialize, Debug)]
enum Test
{
    Inner {val: i32}
}

fn main()
{
    let ser = rmp_serde::to_vec_named(&Test::Inner {val: 10}).unwrap();
    println!("{:?}", ser);
    let de: Test = rmp_serde::from_slice(&ser).unwrap();
    println!("{:?}", de);
}

Serialised form is [146, 0, 129, 10] and it looks invalid.

[cbeck88]

Why would you expect anything different?