# can't get multiple lines with tikz-qtree package

I am using the following code to draw a fairly simple tree. The problem is that the line break commands are being ignored although I have found a number of examples on the net that show that they should work. What I am getting is the figure below. I am not sure where my problem is and would appreciate any help.

\documentclass{article}
\usepackage{tikz}
\usepackage{tikz-qtree}

\begin{document}
\begin{tikzpicture}
\tikzset{level distance=40pt, sibling distance=10pt}

\Tree [. {MapReduce Join \\ Implementations}
[.{Equi-join}
[.{Repartition Join} ]
[.{Semijoin} ]
[.{Map-only Join}
[.{Partition join} ]
]
]
[.{Similarity join} ]
[.{Multi-way join}
[.{Multiple \\ MapReduce \\ jobs} ]
[.{Replicated join}  ]
]
]
\end{tikzpicture}
\end{document}


-

\tikzset{every tree node/.style={align=center,anchor=north}}