Why is a newly created index contains the invalidLSN?

Hello hackers.

I have a small question. While working on an incremental backup I noticed a
strange thing.
Newly created index is contains the invalid LSN (0/0).
Exmaple:
postgres=# select lsn from page_header(get_raw_page('test_a_idx2',0));
 lsn
-----
 0/0
(1 row)

Can you explain me why?

Thanks.

--
Yury Zhuravlev
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company