Nothing changed but CorelDraw implies there is something to save

Nothing changed but CorelDraw implies there is something to save by showing a star beside the document's name and showing the save symbol again (Disk symbol).

This happens just after a while or if I switch between documents.

So I feel compelled to save again and again - because maybe I really changed something!? This unnecessary saving-processes are especially annoying when editing files which need a long time to save.