temporary tables are logged somehow?

Hello all,
I have a problem with growing WAL-files populating a temporary table.

After running the following script 8192 times (each in separate connection)
I can see 3*16 MB WAL files.

CREATE TEMP TABLE IF NOT EXISTS positiontemporarytable (pos_instrument_id
> integer, pos_code varchar(40));
> BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;
> prepare pos_insert (integer, varchar(40)) as insert into
> "positiontemporarytable" values($1, $2);
> execute pos_insert ('76','27958');
> execute pos_insert ('71','9406:58');
>
......

<about 8000 same 'executes' commands>
>
......

execute pos_insert ('74','19406:58');

COMMIT;

It was tested via pgbench:

> pgbench -l -t 8192 -C -f /db/postgres/report_test.sql db_test

and simple bash script:

> for i in {1..8192}
> do
> echo $i
> psql -f /db/postgres/report_test.sql db_test
> done

Results are the same. Server version 9.3.5 (it seems 9.2.4 and 9.2.9 also
affected by this).

As metioned, for example, in Robert Haas blog
http://rhaas.blogspot.ru/2010/05/global-temporary-and-unlogged-tables.html

> 3. They are not WAL-logged.

Whats wrong with it in my case?

--
Regards, Andrey Lizenko