\slurUp with \grace

[Graham Percival]

\slurUp doesn't seem to affect slurs that begin inside a grace.  I tried
using "\property Grace.Slur", but lily complains:
Interpreting music...warning: can't find or create `grace' called `'


----
\score{\notes{ a'4
\slurUp
\grace{
%\property grace.Stem \set #'direction = #1
[b'16( a' g'] } e'4 )fis'
\slurBoth
}}
-----

I'd like to get a slur over the grace notes and into some non-grace notes,
where the slur is over the notes (rather than under, which seems to be the
default).  Any suggestions?

- Graham Percival