SB-28 preflash with slave flash?

[ayu]

Hi,

Say, I am using F5/F90X, SB-28, D lens in 3D multi-sensor balanced fill-flash.  
Moreover, I am also using another flash on a photosensitive slave.  I know SB-28 
will fire preflashes before the shutter "open".  I am wondering if these 
preflashes trigger the slave to fire before the shutter open.  If so, the slave 
become useless.  Am I right?

Thanks in advance,

FS