Editing map widget doesn't visually change it in dashboard

1. Open existing dashboard or create a new one.
2. Create a new map widget.
3. Choose one map.
4. Don't save yet, but choose a different map.

Result: the new chosen map is not displayed, but only visible after save.
Expected: the chosen map is visible.

Note: On my machine and 4.0 even the first map was not visible. And 3.4 works fine.