Use of #h method in a controller

I have rails-2.2.2 installed on 2 different computers and routinely switch back and forth between the two of them. I just wrote some code today on my desktop in which I invoked the #h method inside a controller (because I wanted to sanitize a string prior to saving it in an instance variable). When I got home this evening and pulled the code onto my laptop, I found that I got an undefined method error for h.

Why would it be undefined on one computer but not the other? The only thing that I can think of is that I (most likely) have different sets of gems installed (although both have rails 2.2.2 installed)

Any ideas?