Redmine

I'm upgrading from 1.1.3 to 2.0.3

During the upgrade process, Redmine still complains about the following:
Redmine requires bundler 1.0.21 (you're using 1.0.15). Please install a newer version with 'gem install bundler'

Here's the screenshot of my error when I try to load up Redmine in my browser.
http://www.redmine.org/attachments/download/7591/bundler_error.png

Is this problem with passenger?

Thanks,
Serj