huginn: Problems with session: changing password ends up in HTTP 500 error page

On /users/edit page when I try to change the password for the currently logged in user, I get an HTTP 500 error page.

Relevant part of the log looks like:

11:42:37 web.1 | [b6c1a083-8819-44e3-abf4-4505bf060d56] Started PUT “/users” for 172.17.0.1 at 2016-11-12 12:42:37 +0100 11:42:37 web.1 | [b6c1a083-8819-44e3-abf4-4505bf060d56] Processing by Users::RegistrationsController#update as HTML 11:42:37 web.1 | [b6c1a083-8819-44e3-abf4-4505bf060d56] Parameters: {“utf8”=>“✓”, “authenticity_token”=>“1Ai3W0aT4r2kkKw8BPbRMDWuzKOl/wSGxQdqKMRs97kR6L//BYGEw4VTn6EKUfDQZWnbOQRAQiDEkakVMbfiDg==”, “user”=>{“current_password”=>“[FILTERED]”, “password”=>“[FILTERED]”, “password_confirmation”=>“[FILTERED]”}, “commit”=>“Update”} foreman stdout | 11:42:37 web.1 | [b6c1a083-8819-44e3-abf4-4505bf060d56] Can’t verify CSRF token authenticity. 11:42:37 web.1 | [b6c1a083-8819-44e3-abf4-4505bf060d56] Completed 500 Internal Server Error in 8ms (ActiveRecord: 0.0ms) 11:42:37 web.1 | [b6c1a083-8819-44e3-abf4-4505bf060d56]
11:42:37 web.1 | [b6c1a083-8819-44e3-abf4-4505bf060d56] NoMethodError (undefined method to_key' for nil:NilClass): 11:42:37 web.1 | [b6c1a083-8819-44e3-abf4-4505bf060d56] 11:42:37 web.1 | [b6c1a083-8819-44e3-abf4-4505bf060d56] config/initializers/silence_worker_status_logger.rb:3:in call’