createuser: How to specify a database to connect to

Hi

I'm trying to add a new DB user with the following command from my client machine:
createuser -h my.host.name -U mysuperusername --pwprompt newusername

I'm getting the following message:
createuser: could not connect to database postgres: FATAL: no pg_hba.conf entry for host "10.0.0.1", user "mysuperusername", database "postgres", SSL on

Now, it's true that our pg_hba.conf doesn't allow access to the postgres database. We did this intentionally, as usually no one needs to connect to this database.

So I tried to do
export PGDATABASE=sogis
before the createuser command. But no success. Does anyone know of another way to achieve what I'm trying?

I whish to do it with createuser rather than with the SQL command CREATE USER because this way I can avoid the password for the new user to show up anywhere in the history.

I'm on 9.2 on Ubuntu 14.04.

Thank you very much,
Andi