config-rs: Unable to deserialize unsigned integers

When implementing config::ValueKind for a custom type, the error invalid type: unsigned integer 64 bit '128', expected an signed 64 bit or less integer for key 'inner.unsigned' is thrown if the custom type contains a unsigned integer. The following is a minimum example:

#[derive(Deserialize, Eq, PartialEq, Debug)]
struct Container<T> {
    inner: T,
}

#[derive(Deserialize, Eq, PartialEq, Debug)]
struct Unsigned {
    unsigned: u16,
}

impl Default for Unsigned {
    fn default() -> Self {
        Self { unsigned: 128 }
    }
}

impl From<Unsigned> for config::ValueKind {
    fn from(unsigned: Unsigned) -> Self {
        let mut properties = HashMap::default();
        properties.insert(
            "unsigned".to_string(),
            config::Value::from(unsigned.unsigned),
        );

        Self::Table(properties)
    }
}

assert_eq!(
    Container {
        inner: Unsigned::default()
    },
    config::Config::builder()
        .set_default("inner", Unsigned::default())
        .unwrap()
        .build()
        .unwrap()
        .try_deserialize::<Container<Unsigned>>()
        .unwrap()
);