pg_restore issue

Hi, I'm trying to restore a database dump using pg_restore with the
following parameters:

pg_restore -h 127.0.0.1 -U _postgresql \
  -c -d postgres --exit-on-error \
  my_dump.backup

Note I used "\" to wrap the command, but the real one does not have
those.

pg_restore: [archiver (db)] Error while PROCESSING TOC:
pg_restore: [archiver (db)] Error from TOC entry 3156; 2606 432226 FK
CONSTRAINT fkidturno postgres
pg_restore: [archiver (db)] could not execute query: ERROR:  relation
"public.turnodocumento" does not exist
    Command was: ALTER TABLE ONLY public.turnodocumento DROP CONSTRAINT
fkidturno;

Why is this happening?, should I change the command I'm using to create
the backup?.

To backup the database I'm using:

pg_dump -Fc -h 127.0.0.1 -U postgres mydb > my_dump.backup

P.S.: the original db is PostgreSql 8.4, the target is 9.2

Regards,
--
Leonardo M. Ramé
Medical IT - Griensu S.A.
Av. Colón 636 - Piso 8 Of. A
X5000EPT -- Córdoba
Tel.: +54(351)4246924 +54(351)4247788 +54(351)4247979 int. 19
Cel.: +54 9 (011) 40871877