Encoding problems

Hello,

I have a database in LATIN1 encoding:

neuss@tell:~$ psql -l
                                       List of databases
   Name    |  Owner   | Encoding |    Collation     |      Ctype       |   Access privileges   
-----------+----------+----------+------------------+------------------+-----------------------
 courses   | neuss    | LATIN1   | de_DE.iso-8859-1 | de_DE.iso-8859-1 | 


Accessing it with CLSQL I observe

* It works with the :postgresql db type, however this interface is
  somewhat unstable (SBCL drops in ldb at some place), and the reason
  that it works is that CFFI:*DEFAULT-FOREIGN-ENCODING* is :utf-8.

  (with-database-connection
    (lname (first (select 'student :where [= [id] 713479] :flatp t))))
  => "Böhme"

* It does not work with :postgresql-socket db type (because I have
  set SB-IMPL::*DEFAULT-EXTERNAL-FORMAT* to :latin-1)

  (with-database-connection
    (lname (first (select 'student :where [= [id] 713479] :flatp t))))
  => "Böhme"

* It works setting SB-IMPL::*DEFAULT-EXTERNAL-FORMAT* to :utf-8
  (let ((SB-IMPL::*DEFAULT-EXTERNAL-FORMAT* :utf-8))
    (with-database-connection
      (lname (first (select 'student :where [= [id] 713479] :flatp t)))))
  => "Böhme"

So: Why is my database accessed with UTF-8 encoding?  And how can I
change this?  [I would like to stay with LATIN1 external format, because
my web pages (served by Hunchentoot) are in that encoding.]

Thank you,
Nicolas