[O] org-edit-special cannot tell ditaa from table

[zwz]

Here is an example:

* test
#+BEGIN_SRC ditaa
  +----+  +-----+
  |    |  |     |
  |    |  |     |
  +----+  +-----+
#+END_SRC

When I hit C-c ', the minibuffer says "Recognizing tables...done",
and the org src scratch buffer does not turn picture-mode on.