Cookies are not set on ELB DNS

[sparrovv]

I've been testing server side events for mayflower on temporary ELB domain(https://mayflower-v01-staging-lb-471749990.eu-west-1.elb.amazonaws.com) and it looks that cookie is not persisted in the browser after setting in sinatra response:

#in sinatra
puts response.headers
{"Content-Type"=>nil, "Set-Cookie"=>"_sp_id.3c70=a8bb24cb31a5de50.1481879822.0.1481879822.; domain=.amazonaws.com; path=/; expires=Sun, 16 Dec 2018 09:17:02 -0000"}
# browser console
document.cookie
""

Screen shot from Network tab:

It works on localhost.