Topic: heroku rake db:migrate fails

I want upload some changes to my heroku up, but if I type

heroku rake db:migrate

I got this error:

rake aborted!
Permission denied - /home/slugs/379875_18c20e2_b265-4dc295df-e7e6-4e95-b692-87812981aaa5/mnt/tmp/schema.rb

(See full trace by running task with --trace)
(in /disk1/home/slugs/379875_18c20e2_b265-4dc295df-e7e6-4e95-b692-87812981aaa5/mnt)


Default gems, and config. What's wrong?