[BUG?] Org Mode 20150831, ob-R not working

[thomas <thomas@friendlyvillagers.com>]

Hi There,

updating from Org Mode 20150713 to 20150831 (Elpa package) gives me an 
error at startup:

#+BEGIN_EXAMPLE
Warning (initialization): An error occurred while loading 
`/home/thomas/.emacs':

Invalid function: org-babel-header-args-safe-fn

To ensure normal operation, you should investigate and remove the
cause of the error in your initialization file.  Start Emacs with
the `--debug-init' option to view a complete error backtrace.
#+END_EXAMPLE

And ~emacs --debug-init~ says:

#+BEGIN_EXAMPLE
Debugger entered--Lisp error: (invalid-function 
org-babel-header-args-safe-fn)
   org-babel-header-args-safe-fn((:cache :colnames :comments :exports 
:epilogue :hlines :noeval :noweb :noweb-ref :noweb-sep :padline 
:prologue :rownames :sep :session :tangle :wrap (:eval "never" "query") 
(:results lambda (str) (not (string-match "file" str))) :width :height 
:bg :units :pointsize :antialias :quality :compression :res :type 
:family :title :fonts :version :paper :encoding :pagecentre :colormodel 
:useDingbats :horizontal))
byte-code("\301\302\303\304\b!#\210\305\306\307\310\311\312\313\314\315\316& 
  \207" [ob-R-safe-header-args put org-babel-default-header-args:R 
safe-local-variable org-babel-header-args-safe-fn 
custom-declare-variable org-babel-R-command "R --slave --no-save" "Name 
of command to use for executing R code." :group org-babel :version 
"24.1" :type string] 10)
   require(ob-R)
   ...
   org-babel-do-load-languages(org-babel-load-languages ((awk . t) 
(python . t) (sql . t) (asymptote . t) (scheme \.t) (sh . t) (lilypond . 
t) (R . t) (ditaa . t) (dot . t) (plantuml . t) (C . t) (java \.t) 
(sqlite . t)))
   eval-buffer(#<buffer  *load*> nil "/home/thomas/.emacs" nil t)  ; 
Reading at buffer position 3634
   load-with-code-conversion("/home/thomas/.emacs" "/home/thomas/.emacs" 
t t)
   load("~/.emacs" t t)
   ...
   command-line()
   normal-top-level()
#+END_EXAMPLE

I'm having a problem with R. In my .emacs I load R like this:

#+BEGIN_SRC emacs-lisp
(require 'ess-site) ;; see 
http://orgmode.org/worg/org-tutorials/org-R/org-R.html
(org-babel-do-load-languages 'org-babel-load-languages '((R . t)))
#+END_SRC

If I remove R from babel languages, the Error disappears.

I get the same Error when I require ob-R:

#+BEGIN_SRC emacs-lisp
(require 'ob-R) ;;  Invalid function: org-babel-header-args-safe-fn
#+END_SRC

Huh, this is odd! Am I missing something?
If not, how can I revert to 20150713?



Many thanks,
thomas