Require this in your project.
Add "Fervo\\Composer\\HerokuDb\\HerokuDatabase::populateEnvironment", to your composer.json post-install-cmd and post-update-cmd before the Incenteev handler
Add the following to the incenteev-parameters extra section:

"env-map": {
    "database_driver": "DATABASE_DRIVER",
    "database_host": "DATABASE_HOST",
    "database_port": "DATABASE_PORT",
    "database_name": "DATABASE_NAME",
    "database_user": "DATABASE_USER",
    "database_password": "DATABASE_PASSWORD"
}