This bug says it's closed but it is still there. How do we implement whatever fix there is?
That bug was fixed in EPiServer.CMS.Core version 9.6.1, which was released in update 97 on Jan 22, 2016. So, you should update to the latest version. To learn about updating, see http://world.episerver.com/documentation/Items/Installation-Instructions/Installing-Episerver-updates/.