byobu: Vertical window split issue

Vertical split with default keys configuration in byobu (which is Shift+F2) doesn't work. I decided to change it to Ctrl+F1 instead. To do it open keybinding file:

sudo vim /usr/share/byobu/keybindings/f-keys.tmux

And replace line

bind-key -n S-F2 display-panes \; split-window -v

with

bind-key -n C-F1 display-panes \; split-window -v

Make sure that tmux keybinding is active and default one. Open file

/usr/share/byobu/keybindings/f-keys

and check that it contains

source $BYOBU_PREFIX/share/byobu/keybindings/f-keys.tmux