Babel latex block: setting engine

[Jarmo Hurri]

Greetings.

How do I specify an engine to use in an individual latex Babel block?

Here is an example of the type of block I am having trouble with:

#+begin_src latex :file not-gate.pdf :fit yes :headers 
'("\\usepackage{tikz,circuitikz}") :results output graphics file :cache yes
  \begin{circuitikz}[color=white]
    \ctikzset{logic ports origin=center}
    \draw (0, 0) node [not port,scale=1.7] (notport) {}
    (notport.in) node [anchor=east] {A}
    (notport.center) node {\scriptsize NOT};
  \end{circuitikz}
#+end_src

This block used to compile just fine with pdflatex but now complains

\msg_fatal:nn {fontspec} {cannot-use-pdftex}

and says I have to use either xelatex or lualatex.

All the best,

Jarmo