[luatex] fatal error "invalid DVI command"

[Robert]

Hello,

With luatex 1.07, the following will result in the fatal error "invalid 
DVI command":

\nopagenumbers
%\font\1="cmr10" at 10pt % OK
%\font\1="pbkd8t" at 10pt  % not OK
\font\1="SourceSansPro-Regular-osf-t1" at 10pt % not OK
\1 aaa

\letterspacefont\2\1 100
\2 aaa

\bye

This does not happen with all fonts (maybe something to do with 
re-encoding?), but in any case it used to work in TL17.

Best,
-- 
  Robert