Fontsize with knitr & tikzDevice

Question

I saw there are already a couple of questions on the argument (here and here) but since they are a few months old and since I can't manage to make the option dev.args=list(pointsize=5) works even following the answers I will post it again.

I am trying to decrease the fontsize of my plot labels. But even adding changing the pointsize in the MWE below I can't get the font size change.

\documentclass[a4paper]{article}
\begin{document}

\begin{figure}
<<dev='tikz', dev.args=list(pointsize=5)>>=
x<-1
plot(x)
@
\end{figure}

\end{document}