Error with amsthm package: ! Missing { inserted.T begin{theorem} T

My file is:

documentclass{article}
usepackage[utf8x]{inputenc}
usepackage[english, hebrew]{babel}
usepackage{amsmath}
usepackage{amssymb}
usepackage{amsfonts}
usepackage{amsthm}
newtheorem{theorem}{Theorem}
title{}
author{}
date{}
begin{document}

maketitle
begin{theorem} Text text ... end{theorem}
end{document}

the error is: ! Missing { inserted.T begin{theorem} T

If I remove the usepackage{amsthm} it works but I lose other functionality.

Thanks in advance.