Use of #h method in a controller

I have rails-2.2.2 installed on 2 different computers and routinely
back and forth between the two of them. I just wrote some code today on
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
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?