pg_dump/pg_restore

PostgreSQL 7.3.2

I have been dumping my database with next options:
pg_dump -f /path_to_database/backup/db_backup.file -Z 9 database_name
and get db_backup.file file.

Then a try to restore my data:
pg_restore /path_to_database/backup/db_backup.file
and get next error
pg_restore: [archiver] input file does not appear to be a valid archive

I think it's because in pg_dump, I not set -F c option :(

How I can restore this broken file?

Thanks