I have the problem with heroku

<strong>Gems</strong>

Rails 3.2.16
Mongoid 3.1.6
Moped 1.5.1

<strong>config/mongoid.yml</strong>

production:
sessions:
default:
uri: <%= ENV['MONGOHQ_URL'] %>
options:
skip_version_check: true
safe: true

when I try to run the command

heroku run rake db:mongoid:create_indexes

I have got the error

Running rake db:mongoid:create_indexes attached to terminal... up, run.1616 rake aborted!
The operation: #<Moped::Protocol::Commands::Authenticate
@length=155
@request_id=3
@response_to=0
@op_code=2004
@flags=[]
@full_collection_name="app21238711.$cmd"
@skip=0
@limit=-1
@selector={:authenticate=>1, :user=>"...", :nonce=>"...", :key=>"..."}
@fields=nil>
failed with error 18: "auth fails"