Fuctions in c-mode-hook being called twice?(24.3.92)

[address@hidden]

emacs -Q
Then run the following code:
(defun my-test-func ()
  (message "hook test")
  )

(add-hook 'c-mode-hook 'my-test-func)

Open a c file. Go to the *Message* buffer. "hook test" is printed twice.