eval-after-load causes void-variable error

[Sean McAfee <eefacm@gmail.com>]

For a long time I had this in my .emacs file:

(require 'ffap)
(add-to-list 'ffap-alist (cons +my-ffap-regexp+ #'my-ffap-hook))

I recently decided to optimize it a bit and changed it to:

(eval-after-load 'ffap
  '(add-to-list 'ffap-alist (cons +my-ffap-regexp+ #'my-ffap-hook)))

Now, however, as soon as the ffap command is activated, I get an error:

Lisp error: (void-variable ffap-alist)

Somehow, using eval-after-load is causing the variable ffap-alist to be
unbound, or not bound in the first place.  Does anyone have any idea
what's going on?