Error when calling describe-variable/key/function() in help-fns+.el

[Nordlöw]

I get the following error:

Debugger entered--Lisp error: (void-function describe-simplify-lib-
file-name)
  describe-simplify-lib-file-name(nil)
  describe-variable(nil nil nil)
  call-interactively(describe-variable nil nil)

when I try to use describe-variable()

I searched for describe-simplify-lib-file-name in my emacs configs and
found it in only once in help-fns+.el.

Then I looked into lisp/Changelog and found the following entry that
mentions describe-simplify-lib-file-name(). I am using Emacs version
23.0.60.1.

2008-09-01  Martin Rudalics  <rudalics@gmx.at>

        * help-fns.el (describe-simplify-lib-file-name)
        (find-source-lisp-file): Removed.
        (find-lisp-object-file-name): New function giving preference to
        files found via load-path instead of loaddefs.el.
        (describe-function-1): Use new function instead of the removed
        ones.  (Bugs #587, #669, #690)
        * faces.el (describe-face): Use find-lisp-object-file-name instead
        of describe-simplify-lib-file-name.

Thanks in advance,
Nordlöw