Asterisk intsall error

Fresh install of Slackware 11 using kernel. The latest libpri and zaptel from the 1.2 series compile and install without error. When I get to Asterisk however I get this error:

NG -DCRYPTO -fPIC -c -o chan_phone.o chan_phone.c
In file included from chan_phone.c:40:
/usr/include/linux/ixjuser.h:351: error: syntax error before ‘*’ token
make[1]: *** [chan_phone.o] Error 1
make[1]: Leaving directory `/root/dls/asterisk-1.2.18/channels’
make: *** [subdirs] Error 1

By Googling I found out how to fix this by adding a line to the chan_phone.c file but I really have no clue what that does I’d really like to know why it is happening - can someone explain?

Well as usual, shortly after posting something I find a fix. I removed the kernel-header package and restored the stock 2.4 kernel-headers package and all is well. I look forward to the upcoming slack release which will finally use a 2.6 kernel by default.