How to set a Twig template variable that has a period in it

This:

{% if is_front %}
  {% set page.navbar_branding = '' %}
{% endif %}

Results in this:

[Mon Sep 17 11:58:59.989978 2018] [proxy_fcgi:error] [pid 17624:tid 140127653320448] [client 192.168.42.1:55090] AH01071: Got error ‘PHP message: Uncaught PHP Exception Twig_Error_Syntax: “Unexpected token “punctuation” of value “.” (“end of statement block” expected).” at themes/custom/family_home/src/templates/layout/page.html.twig line 17\n’, referer: http://www.family-home.local/

This fixes it:

{% if is_front %}
  {%
    set page = page|merge({
      'navbar_branding': '',
    })
  %}
{% endif %}