Since upgrading from Fedora24 to 25 (now running xfce4-terminal-0.8.5.1-1.fc25.x86_64), the --tab option no longer works if I already have a pre-existing xfce4-terminal window open.  


[netllama@netllama ~]$ xfce4-terminal --tab
[netllama@netllama ~]$ echo $?
0


I would expect a new tab to be opened in the pre-existing window (or at least a new window with a tab opened).