Setting win-options in custom preset

[kaatish]

What is the proper way to set the win_options in a custom preset? I want to replicate this functionality
let bar.win_options['window-status-activity-attr'] = 'bold' using g:tmuxline_preset.

let g:tmuxline_preset = {
\ 'a': '[#S]',
\ 'win': '#I:#W#F',
\ 'cwin': '#I:#W#F',
\ 'win-options': {
\ 'window-status-activity-attr': 'bold'},
\ 'options': {
\ 'status-justify': 'left'}
\ }

The status-justify option is reflected, however the window-status-activity-attr is not. How do I make sure it is?