straight-flag and no-flag

[ljc]

dear list,

i realized that \override Stem #'flag-style = #'no-flag doesn't work  
when using \override Stem #'flag-style = #modern-straight-flag

i'm using the new straight flags in my score, but at certain part i  
need stems without flags in order to conect chords across staves,  
according to the snippet in the user manual (2.2.1 - Cross-staff stems).

here's the code that reproduce what i understand might be a bug:

\version "2.12"

\relative c' {
        \autoBeamOff
        \override Stem #'flag-style = #modern-straight-flag
        g'8 g g g g g g g |
        \override Stem #'flag-style = #'no-flag
        g8 g g g g g g g |
}

how could i solve this?

by the way, straight-flags are mentioned in the news, but as far as i  
can see are otherwise undocumented. at least i haven't been able to  
find any reference in the user manual (or any other manual, for that  
matter).

best,

lj