I can not set created_at attribute in blueprint

[Lewy]

machinist_mongo (1.1.1) mongoid (2.0.0.beta.20 4ef5fd0) mongo (1.1.5) rails 3.0.1

Code: https://gist.github.com/776097

If I create @radar_traffic it always has created_at = Time.now not Time.new(2008). When I add attr_accessible :created_at to my model it works. I try to resolve this problem buy writing in my spec

@radar_traffic = Radar.make(:near_poznan3) @radar_traffic.created_at = Time.new(2008)

but it also doesn't work