tstzrange with ... 'infinity'] + upper_inf() using 9.2.4

Hi,

> select upper_inf(tsrange('2013-05-01'::timestamp, 'infinity'::timestamp, '[]'));
upper_inf
-----------
f
(1 row)

As far as I understood the docs, this query should return true, as the upper bound includes 'infinity'?

[http://www.postgresql.org/docs/9.2/interactive/functions-range.html]
"The lower and upper functions return null if the range is empty or the requested bound is infinite. The lower_inc, upper_inc, lower_inf, and upper_inf functions all return false for an empty range."

[http://www.postgresql.org/docs/9.2/interactive/rangetypes.html]
"Also, some element types have a notion of "infinity", but that is just another value so far as the range type mechanisms are concerned. For example, in timestamp ranges, [today,] means the same thing as [today,). But [today,infinity] means something different from [today,infinity) — the latter excludes the special timestamp value infinity.
The functions lower_inf and upper_inf test for infinite lower and upper bounds of a range, respectively."

Regards
Ralph