Codeship - heroku continous deployment: Push failed: could not store slug!

Trying to deploy automatically form codeship to heroku I was getting the error:

-----> Compressing... done, 72.0MB
-----> Launching...!     
Push failed: could not store slug!     
If the problem persists, see http://help.heroku.com and provide Request ID 

I solved the issue by adding the heroku url project and enable the "force push" flag in the option: Project settings > Deployment > Heroku Deployment > more options.

Reference:
http://stackoverflow.com/questions/9794413/failed-to-push-some-refs-to-githeroku-com