|xinput list-props 8 (my mouse ID) libinput Middle Emulation Enabled (291): 1|
While the next string from the output says:<http://forums.debian.net/viewtopic.php?f=6&t=140901&p=693554#>
|libinput Middle Emulation Enabled Default (292): 0|Seems that .xsessionrc doesn't work now and that's a bug, I guess. But I don't know what package might have caused this issue.