`\not` does not work with unicode-math

Question

I’m using TeXLive 2015 and compile with lualatex or xelatex.

When loading the unicode-math package, the command \not produces a ‘6’ instead of striking through stuff (as in ‘ø’ with \not o).

The following example code

\documentclass{scrreprt}
\usepackage{
    fontspec,
    unicode-math,
}


\begin{document}
    $\not o$.
\end{document}

produces the following output:

I tried to googe this, but couldn’t find any results. It seems unusual that noone else had this issue before – is this intended behaviour? If so, how do I get what I what, namely a ‘ø’ (and actually, I need the result of \not \mapsto)?

I have uploaded a paste of a compiilation’s log under http://pastebin.com/bdinUAT2.