tikz error with `\draw` command and babel package

Question

I'm compiling a document with class article, in which I use tikz library with this libraries:

\usetikzlibrary{arrows,automata,positioning}

And I have this picture (and nothing more in the document):

\begin{tikzpicture}
\node[abstrtz,very thick,rounded corners=0.3cm] (Msg) 
{
Mensaje\includegraphics[scale=0.04]{imgs/unlock.png}
};
\node[abstrtz,very thick,rounded corners=0.3cm,right of =Msg, node distance = 3cm] (MsgC) 
{
Mensaje\includegraphics[scale=0.04]{imgs/lock.png}
};
\draw[->] (Msg) -- (MsgC);
\end{tikzpicture}

I'm compiling it with XeLaTeX. If I comment the \draw... line, it compiles perfectly and displays both nodes. abstrtz is a node defined like:

\tikzset{
  abstrtz/.style = {
    rectangle, rounded corners=0.5cm,
    draw = BGColoro, fill = BGColor, line width = 2pt,
    minimum height = 2em, inner sep = 10pt,
  },
}

However trying to compile with that line, it throws the error: ERROR: Argument of \language@active@arg> has an extra }.

I have observed that if I comment the use of the babel package, it works, and properly displays the arrow. Why is this? Is this normal, and is there a way to fix it?

I was using babel package set in spanish:

\usepackage[spanish]{babel}

Changing that line with \usepackage[latin1]{inputenc} apparently works because I was using nothing else of the babel package than being able to type the characters á, é, í, ó, ú...