Userdata type unknown by name in Gluon

cargo run -q

error: Type `MyUserdata` is not defined
- <example>:3:25
  |
3 |         type Foo = { x: MyUserdata }
  |                         ^^^^^^^^^^
  |

Cargo.toml

[package]
name = "gluon_userdata"
version = "0.1.0"
edition = "2018"

[dependencies]
gluon = "0.13.1"
gluon_codegen = "0.13.1"
gluon_vm = "0.13.1"

main.rs

extern crate gluon;
#[macro_use]
extern crate gluon_codegen;
#[macro_use]
extern crate gluon_vm;

use gluon::import::add_extern_module;
use gluon::{vm, Thread, ThreadExt};
use gluon_vm::api::UserdataValue;

fn main() {
    std::process::exit(match run() {
        Ok(_) => 0,
        Err(e) => {
            eprintln!("{}", e);
            1
        }
    });
}

fn run() -> Result<(), Box<dyn std::error::Error>> {
    let vm = gluon::new_vm();
    vm.register_type::<MyUserdata>("MyUserdata", &[])?;
    add_extern_module(&vm, "make_userdata", load_userdata);

    let v = vm.run_expr::<UserdataValue<MyUserdata>>(
        "example",
        r#"
        let make_userdata = import! make_userdata
        type Foo = { x: MyUserdata }
        let foo = { x = make_userdata 1 }
        foo.x
        "#,
    )?;

    println!("Got result: {:?}", v);

    Ok(())
}

fn load_userdata(vm: &Thread) -> vm::Result<vm::ExternModule> {
    vm::ExternModule::new(vm, primitive!(1, make_userdata))
}

#[derive(Clone, Debug, Trace, Userdata, VmType)]
#[gluon(vm_type = "MyUserdata")]
struct MyUserdata(i32);

fn make_userdata(v: i32) -> MyUserdata {
    MyUserdata(v)
}