Install problems with i4b

[Peter Reimer]

Hello,

I'm trying to install Hans Peter's ISDN4BSD package. I've done
all steps that you see with "make help".

make install
make install_mod

I've added the listed lines in my kernel config and tried to compile
the kernel. But the process stops with this error message:

/usr/src/sys/i4b/driver/i4b_rbch.c: In function `rbch_setup_ft':
/usr/src/sys/i4b/driver/i4b_rbch.c:637: warning: implicit declaration of function `callout_init_mtx'
/usr/src/sys/i4b/driver/i4b_rbch.c:637: warning: nested extern declaration of `callout_init_mtx'
*** Error code 1

Stop in /usr/obj/usr/src/sys/mykernel.
*** Error code 1

Stop in /usr/src.
*** Error code 1

Stop in /usr/src.

Any ideas?
Thanks in advance,
Peter

PS
I'm running FreeBSD 5.3R