Heroku deployment error

[siwka]

Did I miss an instruction in book?

heroku[web.1]: State changed from starting to crashed

/app/vendor/bundle/ruby/2.6.0/gems/bundler-1.17.3/lib/bundler/rubygems_integration.rb:408:in `block (2 levels) in replace_gem': Error loading the 'sqlite3' Active Record adapter. Missing a gem it depends on? sqlite3 is not part of the bundle. Add it to your Gemfile. (LoadError)

Solution: replace sqlite3 to postresql in database.yml production section