TikZ example involving Spies won't typeset properly using XeLaTeX

Question

The example in this answer, illustrating the use of "spies" using the Tikz package, fails to typeset correctly when using XeLaTeX: the magnification circle appears empty. Using pdfLaTeX and LaTeXmk works fine, otherwise.

Do I need to configure my TeX distribution somehow in order to typeset TikZ code using XeLaTeX? (Currently using MacTex 2011 with TeXworks, on OS X Lion.)

Answer 1

There indeed seems to be a problem with the use of "spies" under XeLaTeX. Consider the following MWE, which is a stripped-down version of the answer referred to by the OP:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{spy}
\pagestyle{empty}
\begin{document}
\begin{figure}
\begin{tikzpicture} 
  [spy using outlines={circle, magnification=4, 
   size=1cm, connect spies}]
\draw[help lines] (0,0) grid (2,2);
\draw[red] (0,0) -- (1,1);
\spy [blue] on (1,1) in node at (1.75,2.75);
\end{tikzpicture}
\end{figure}
\end{document}

When compiled under pdflatex, the following figure results:

In contrast, when the same program is compiled under XeLaTeX, one gets:

I.e., both the "cross-hairs" and the red line that terminates in the middle of the "target" aren't shown inside the spy-circle. :-(