[luatex] math font setting

[Herbert Voss]

Hi all,

\input luaotfload.sty
\font\testA={name:TG Pagella Math:mode=base;script=math} at 12pt

%\Umathspaceafterscript\crampedscriptstyle=1pt

\textfont0=\testA Pagella:
$ {1 \over x^2} $
\bye

has the output

-----------------
This is LuaTeX, Version beta-0.70.2-2012052410 (TeX Live 2012)
  restricted \write18 enabled.
(./Namenlos-4.tex
(/usr/local/texlive/2012/texmf-dist/tex/luatex/luaotfload/luaotfload.sty

[ ... ]

! Math error: parameter \Umathspace_after_script\crampedscriptstyle is 
not set.
l.7 $ {1 \over x^2} $

?
------------------

is that the intended behaviour? Or shouldn't \Umathspaceafterscript
not set by LuaTeX?

Herbert