No, you did not do something wrong. At least, not via that login attempt. Interestingly, it's giving the oid in the error, not the dbname, which (IIUC) suggests InitPostgres() is being called by a not-usual path, (e.g. bgworker). Can you login to other databases on that cluster? Do you have any extensions enabled? (if so, try commenting them out and restarting).
Cheers,
Greg
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Enterprise Postgres Software Products & Tech Support