undefined method `seed'

hello,
I am trying to deploy a rails 3.1 app to Heroku and need to run
db:seed
My seeds file has this code

User.seed do |s|
  s.email = "temp@temp.com"
  s.password = "bigsecret"
  s.password_confirmation = "bigsecret"
end

Running rake db:seed locally works fine, but after deployment to
Heroku I try to run this seed file and get error:

undefined method `seed' for #<Class:0x00000006499ac0>

Any ideas why Heroku does not like my seed file?

thanks

Pls try out this heroku:rake:db:seed

Opps my mistake try out this heroku rake db:seed

heroku:rake:db:seed
command does not exist. Are you sure about this sintax?

I did. This is the code that has problems, that I described in first post.
Running heroku rake db:seed is what caused the problem in the first place.