[O] graphviz dot block export and evaluate

[Dmitri Makarov]

Hi all,

Has anyone successfully exported and evaluated src blocks with graphviz dot 
code?
I'm trying to export this block

   #+BEGIN_SRC dot :export both
     digraph G {
       A -> B
     }
   #+END_SRC

and I'm getting the error

org-babel-exp processing...
executing Dot code block...
file-name-extension: Wrong type argument: stringp, nil

How do you debug such problems?

Regards,

Dmitri