"db/development.sqlite3" does not exist

I'm trying to move from sqlite to postgres so I can use Heroku.

My database.yml currently looks like this:

default: &default
  adapter: postgresql
  pool: 5
  timeout: 5000

development:
  <<: *default
  database: db_development

test:
  <<: *default
  database: db_test

production:
  <<: *default
  database: db_production

I have run rake db:create db:migrate but I get this error:

FATAL: database "db/development.sqlite3" does not exist Run `$ bin/rake db:create db:migrate` to create your database

This is confusing given db/development.sqlite3 no longer exists in database.yml. It was replaced by db_development. There's also no mention of sqlite3 in my gem file.