On 2019-03-08 17:38:33 +0000, PG Bug reporting form wrote:
> The following bug has been logged on the website:
>
> Bug reference: 15678
> Logged by: Vasiliy Korotkikh
> Email address: dhaenoor@yandex.ru
> PostgreSQL version: 11.2
> Operating system: Debian Stretch
> Description:
>
> In the configuration file of my server there is the following line:
> default_transaction_isolation = 'serializable'
Did you reload the configuration after making that change? SELECT
pg_reload_conf();
Greetings,
Andres Freund