[slime-devel] `slime-mode-hook' customization not working

I have the following in my ~/.emacs:

(add-hook 'slime-mode-hook '(lambda () (local-set-key "\C-c\C-w\C-w" 'insert-wrapping-sexp) (slime-autodoc-mode t)))

But in a lisp buffer C-c C-w C-w still runs `slime-calls-who' instead of clobbering that binding - which is what I want it to do. I can't use slime-calls-who (I'm using SBCL) and even if I could, I use C-c C-w C-w so much for `insert-wrapping-sexp' that I'd want to bind slime-calls-who to something else.

According to the manual (section 7.1.1, pg. 18) customizations like the one above are supposed to go in `slime-mode-hook'.

Is there any way I can fix this? Am I missing something stunningly obvious?

Thanks in advance.