Tmux - ambiguous option: mouse error

Question

I recently updated my OS X El Capitan (version 10.11.1) and my tmux (version 1.9a via Homebrew) mouse mode stopped working. I get the error:

/Users/username/.tmux.conf:57: ambiguous option: mouse

On line 57 of my tmux.conf, I have the following code to enable mouse mode:

set -g mouse on

And the the following lines to enable/disable mouse mode:

# Toggle mouse on
bind m \
    set -g mouse on \;\
    display 'Mouse: ON'

# Toggle mouse off
bind M \
    set -g mouse off \;\
    display 'Mouse: OFF'

# Start copy mode when scrolling up or down
bind -n WheelUpPane copy-mode
bind -n WheelDownPane copy-mode

I previously had to update mouse-mode to mouse to fix the mouse mode when I updated tmux. I tried reverting that fix with no success. Any help would be greatly appreciated!

Answer 1

The new mouse mode (i.e. the one you're activating in your config) became available with tmux 2.1, see the changelog for details. Updating to the latest version should resolve your issue.