I installed upgrades to libreoffice on Debian 9 stretch, using XFCE 1.2. Installed version 5.4 over old 5.2 (I think) and installed version 6.0 for the first time. Then there were a couple of old versions left over, so I uninstalled them. Everything is fine, except when I do an alt-tab, the icon for a running libreoffice program, such as Writer, is the default system icon, just a rectangle with a bar at the top, as though no icon is assigned to the program. Tried reinstalling 6.0 and rebooting to no avail. How do I get my libreoffice specific icons back. A bit of a nuisance when using alt-tab and trying to get back to my Writer instance. No results doing google search or at this forum. Any ideas? Many thanks.