[Rails v3] time_zone_select :priority_zones not working properly

When using :priority_zones for time_zone_select in a manner described
by the API docs for ActionView::Helpers::FormOptionsHelper I'm getting

Here is an API docs example:
time_zone_select( "user", 'time_zone', TimeZone.us_zones, :default =>
"Pacific Time (US & Canada)")

When using this code I get "uninitialized constant

The first thing I noticed was that TimeZone is camel cased. This seems
confusing to me considering TZInfo::Timezone is proper cased. I tried
using proper cased Timezone and continued to get the same error. Next,
I tried using TZInfo::Timezone, this worked.

time_zone_select( "user", 'time_zone',
TZInfo::Timezone.us_zones, :default => "Pacific Time (US & Canada)")

It seems that I'm either doing it wrong, there is a different way to
do it in Rails 3.0, the documentation is wrong, or there is a bug
(understandable since I'm using Rails 3.0 beta).

Can anybody shed light on this?

Documentation: http://api.rubyonrails.org/classes/ActionView/Helpers/FormOptionsHelper.html#M001626