NameError with RDiscount

I installed the RDiscount gem to my project.

When I try to put the following in my application_helper.rb:

RDiscount.new(text).to_html  

I get

NameError:  
uninitialized constant ApplicationHelper::RDiscount

In the irb I can get RDiscount working after requiring it, but I can't get 开发者_运维技巧it to function anywhere in my project. What's wrong?

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Have you put gem "rdiscount" in your Gemfile, updated and restarted your server? I got this error when I forgot to restart the server.