Change effective on 16 July 2019
Heroku is deprecating support for all databases running PostgreSQL 9.4. This deprecation is part of our documented version support policy. You will no longer be able to create new PostgreSQL 9.4 databases. Creation of forks and followers of existing databases is still supported.
Deprecated Postgres databases will be automatically migrated to the latest version of Postgres from end of November 2019. We urge customers to upgrade their database themselves prior to this date so that they can test application compatibility and perform the migration on their own schedule.