# How to use xymatrix with a0poster? [duplicate]

I want to make a DIN-A0 poster using the documentclass a0poster. Why can't I draw diagrams in that documentclass? The MWE below crashes and I don't know how to fix that. :(

MWE:

\documentclass[a0,portrait]{a0poster}

\usepackage{amsfonts, amsmath, amscd, amssymb}
\usepackage{graphicx}
\usepackage{xy}

\begin{document}

\begin{align*}
\xymatrix{A & B}
\end{align*}

\end{document}