random(4) confusions

[no at spam at mgedv.net]

hi,

if i run man 4 random, i'll get the following:

     The kern.random.sys.burst variable instructs the kernel thread that
pro-
     cesses the harvest queue to tsleep(9) briefly after that many events
have
     been processed.  This helps prevent the random device from being so
com-
     pute-bound that it takes over all processing ability.  A value of 0
     (zero) is treated as infinity, and will only allow the kernel to pause
if
     the queue is empty.  Only values in the range [0..20] are accepted.

if i try to read/set this setting, sysctl returns:
sysctl: unknown oid 'kern.random.sys.burst'

what's wrong, my kernel or the manpage?
[6.1-RELEASE/i386]