Latex: Unmatched braces in tikz matrix node

I just struggled to get some tikz code working which looked approximately like this:

\matrix { a & b & c \\ d & e & f };

This fails to compile with warning:  "Missing } inserted."


The problem turned out to be that the matrix command in tikz always needs to end with a new line, that is:

\matrix { a & b & c \\ d & e & f \\};