Modern-straight-flag

[Jethro Van Thuyne]

I can find some references to the Stem-property "modern-straight-flag" and 
"old-straight-flag" on the net, yet I cannot get them to be displayed.

I have tried:

 \layout {
   \context { \Score 
     \override Stem #'flag-style = #modern-straight-flag 
   } 
 } 

in an external stylesheet or within the file itself, both without success 
yet without any parsing errors either. I have also tried (to no avail, of 
course) putting the override in the Staff and Voice context.

Wherever I declare the override, I get the normal classical flags. Apart 
from that, [#'flag-style = #'mensural] and [#'flag-style = #'no-flag] DO 
work. I presume I'm missing out on something. Is there anyone who can 
help?

Best regards,

Jethro.