Calling an undefined method in a controller doesn't raise an error

When calling an undefined method on a controller class, no error is raised. The routes just stop working.

For example:

class ApplicationController < ActionController::Base
  test123
end

Or:

class PeopleController < ApplicationController
  test123
end

These does not raise a NoMethodFound exception and the log just says "ActionController::RoutingError (No route matches "/people")".
The route does exist in routes.rb of course...
I'm running Ruby 1.9.1.