tuplet number

[Alex Jones]

I am using the expression to not display the tuplet number
\override TupletNumber #'stencil = ##f

but at some point later in the score I want that number to be displayed again 
and when I use what I figured was the appropriate reactivation expression
\override TupletNumber #'stencil = ##t
it works but I get the error
warning: type check for `stencil' failed; value `#t' must be of type `unknown'
Is this a problem, or should I be using a different statement?

Thanks!

-akj
--
Alex K. Jones - clarinet
www.jeffsys.net/~akjones/music
847-372-8999