Error raised with node [closed]

Question

I have the following code that raises "undefined control sequence" error on the line that draws redarrow. When I continue with compilation, it does produce the red arrow, but gives this error that I can't figure out.

\documentclass{scrartcl}        

\usepackage{tikz}

\usetikzlibrary{shapes,positioning,arrows}
\tikzstyle{redarrow}=[->, >=triangle 90,dashed, red]

\tikzstyle{every entity} = []
\tikzstyle{smentity} = [rectangle, draw, black, 
                      minimum width=4em, minimum height=2em,
                      every entity]

\begin{document}
\begin{tikzpicture}[node distance=1cm, every edge/.style={link}]


\node[smentity] (d1) {1111 1101};

\draw[redarrow] (d1.130) -- ++(0,0.4) node[above]{\alert{11101}} -|  (d1.35);


\end{tikzpicture}
\end{document}