How to implement Gtk 4 Rust file drag and drop?

I have been trying to implement a simple drag and drop application in Gtk 4 Rust but I am unable to implement a working version. I can see connect_accept getting triggered, but no matter the result, connect_drop is never triggered when I drag a file from Dolphin to the window. Is there somewhere a working version available?

use gtk::prelude::*; // <- includes Cast, WidgetExt, etc.
use gtk::{Application, ApplicationWindow, Label, DropTarget};
use gtk::glib::Type;
use gtk::gio::prelude::*;
use std::path::PathBuf;
use gtk::gdk::DragAction;
use gtk::glib::clone;
use gtk::glib;

fn main() {
    let app = Application::builder()
        .application_id("com.example.gtk4-dnd-file")
        .build();

    app.connect_activate(build_ui);
    app.run();
}

fn build_ui(app: &Application) {
    let label = Label::builder()
        .label("Drag a file onto this window")
        .margin_top(20)
        .margin_bottom(20)
        .margin_start(20)
        .margin_end(20)
        .build();

    let window = ApplicationWindow::builder()
        .application(app)
        .title("GTK4 Drag & Drop (File)")
        .default_width(400)
        .default_height(200)
        .child(&label)
        .build();

    let drop_target = DropTarget::new(gtk::gdk::FileList::static_type(), DragAction::COPY);


    // Use accept to preview and asynchronously read the value type using read_value_future
    let label_weak = label.downgrade();
    drop_target.connect_accept(move |_target, drop| {
        eprintln!(
            "accept: actions = {:?}, formats = {:?}",
            drop.actions(),
            drop.formats()
        );
        true
    });
    //let drop_target = DropTarget::new(gtk::gdk::FileList::static_type(), gtk::gdk::DragAction::COPY);


    let label_for_drop = label.clone();

    drop_target.connect_drop(move |_target, value, _x, _y| {
        println!("Drop target received value type: {:?}", value.type_());


        label_for_drop.set_label("Drop did not contain a usable file.");
        false
    });


    window.add_controller(drop_target);
    window.show();
}