Thanks for you reply. Reinstalling does not help until I follow
http://emacs.stackexchange.com/questions/28441/org-mode-9-unable-to-eval-code-blocks
, remove all *.elc in the org directory and byte-compile all again.

Best regards,
Ivan

On Mon, Dec 12, 2016 at 5:34 AM, Nicolas Goaziou <mail@nicolasgoaziou.fr>
wrote:

> Hello,
>
> Jiajian Huang <ispinfx@gmail.com> writes:
>
> > After update to org 9.0, the source code block can't no longer be
> exported
> > and
> > org alerts an error.
> >
> > The minimal config I use is
> >
> > (package-initialize)
> >
> > (setq debug-on-error t
> >       debug-on-signal nil
> >       debug-on-quit nil)
> >
> > (require 'org)
> >
> > where the org is installed by elpa.
> >
> > The test.org file contains
> >
> > #+BEGIN_SRC latex :results drawer :exports results
> >   \begin{eqnarray}
> >     a + b = c \label{eq1}
> >   \end{eqnarray}
> > #+END_SRC
> >
> > ONLY. Running C-c C-e l l gives error
> >
> > Debugger entered--Lisp error: (wrong-type-argument stringp nil)
>
> I cannot reproduce it. I suspected an installation that went wrong. You
> could try to remove Org completely and install it again.
>
> Regards,
>
> --
> Nicolas Goaziou
>