# arrows with same length between spaces

I have a problem regarding code in latex. The problem is that the length of the arrows are different depending on the length of the labeling of the maps. e.g. the map {f_{x_0}} has an arrow which is longer than the map {g_*}. Is there a way to fix this? And is there a way to make the arrow a little longer, they are very short.

\begin{equation*}
\pi_1(X,x_0) \xrightarrow{f_{x_0}}  \pi_1(Y,y_0) \xrightarrow{g_*} \pi_1(X,x_1) \xrightarrow{f_{x_1}} \pi_1(Y,y_1)
\end{equation*}

• Please always show a complete document or at least mention the packages you are using. This was tagged tex-core but \xrightarrow is not defined by TeX or even latex by default. – David Carlisle Dec 2 '14 at 15:34

\documentclass{article}

\usepackage{mathtools}
\begin{document}

\begin{equation*}
\pi_1(X,x_0) \xrightarrow{\mathmakebox[1.5cm]{f_{x_0}}}
\pi_1(Y,y_0) \xrightarrow{\mathmakebox[1.5cm]{g_*}}
\pi_1(X,x_1) \xrightarrow{\mathmakebox[1.5cm]{f_{x_1}}}
\pi_1(Y,y_1)
\end{equation*}

\end{document}