fulltext parser strange behave

Hello

I am writing tsearch2 wrapper and I testing functionality. I found
some little bit strange on default parser. It can't parse tags with
numbers:

test=# select * from parse('<h1>zluty kun se napil <b>zlute</b> vody</h2>');
tokid | token
-------+-------
12 | <
3 | h1
12 | >
1 | zluty
12 |
1 | kun
12 |
1 | se
12 |
1 | napil
12 |
13 | <b>
1 | zlute
13 | </b>
12 |
1 | vody
12 | < <=====
19 | /h2
12 | > <=====
(19 rows)

It is correct?

Regards
Pavel Stehule