glib mainloop integration?

I use a zbus ObjectServer inside an application based on Glib's mainloop. Up to zbus 2.0.0-beta.3 I could just plug the file descriptor of zbus::Connection into glib with

pub fn source_add_connection_local<F: FnMut(&zbus::Message) + 'static>(
    connection: zbus::Connection,
    mut on_message: F,
) -> SourceId {
    let fd = connection.as_raw_fd();
    glib::source::unix_fd_add_local(
        fd,
        glib::IOCondition::IN | glib::IOCondition::PRI,
        move |_, condition| {
            debug!("Connection {file_descriptor} entered IO condition {:?}");
            match connection.receive_message() {
                Ok(message) => on_message(&message),
                Err(err) => error!(
                    log,
                    "Failed to process message on connection {}: {:#}", fd, err,
                ),
            }
            glib::Continue(true)
        },
    )
}

In the on_message callback I'd simply dispatch the message to the object server.

As of zbus-2.0.0-beta.4 this no longer works; for some reason the file descriptor never even enters the IN condition. In other words I never see the debug! log from above. I tried to make sense of the diff between beta.3 and beta.4, but it looks as if beta.4 migrated to async connections and I'm somewhat unfamiliar with async Rust.

Am I missing something obvious? What's the recommended way to integrate a zbus object server into an external event loop?