Entering a minor mode with a major mode in Emacs

Question

This question may be a duplicate of this question, but I can't get the following to work properly in my emacs.

I am trying to enter minor mode mlint-mode whenever I enter major mode matlab-mode (both modes available at their SourceForge page). I have the following in my .emacs file:

(add-hook 'matlab-mode-hook
      (function (lambda()
                  (mlint-mode))))

which looks like the answer to the question I linked above. When opening a .m file, I get the following error:

File mode specification error: (void-function mlint-mode)

Could someone please assist in helping me write the correct hook to enter mlint-mode when I open a .m file? FWIW, I'm running emacs 23.1.50.1.