pgsql exception: argument may not be null or empty

[marcelo-ni]

Error occurs from Npgsql through LinqPad.Postgresql.Driver 0.3, against posgresql 9.4.12.
In the driver´s screen I set up the connection string as
Host=xxx.xxx.xxx.xxx;Port=5432;Database=xxxxxx;Username=postgres;Password=xxxxxxx;
In same screen, "Test connection" is successful, but when I try to connect the error brings up.
May be an issue from the LinqPad driver?