I just got this compile problem in trying to compile a kernel:

  Machine: pc532
  SUP: Dec 18 sup date

cc  -c -O -msb -I. -I../../../.. -I../../../../sys -I../.. -DTIMEZONE="0" -DDST="0" -DSWAPPAGER -DVNODEPAGER -DDEVPAGER -DKTRACE -DFIFO -DCOMPAT_43 -DTCP_COMPAT_42 -DCOMPAT_09 -DCOMPAT_10 -DFFS -DNFSSERVER -DNFSCLIENT -DFDESC -DKERNFS -DINET -DCOMDEF_SPEED=B19200 -DCONFIG_NEW -DKERNEL  ../../../../miscfs/fifofs/fifo_vnops.c
../../../../miscfs/fifofs/fifo_vnops.c:77: `vop_lease_desc' undeclared here (not in a function)
../../../../miscfs/fifofs/fifo_vnops.c:77: initializer element for `fifo_vnodeop_entries[11].opve_op' is not constant
../../../../miscfs/fifofs/fifo_vnops.c:77: warning: `struct vop_lease_args' declared inside parameter list
../../../../miscfs/fifofs/fifo_vnops.c:77: warning: its scope is only this definition or declaration,
../../../../miscfs/fifofs/fifo_vnops.c:77: warning: which is probably not what you want.
*** Error code 1

Stop.