ipf 4.1.7, compilation error in ip_pptp_pxy.c

Compilation of ipf 4.1.7 in Solaris with Sun Workshop 5.0 cc fails:
cc -Xa -xildoff -I. -O -I../.. -D_BSD_SOURCE -DSOLARIS2=7 -DIPFILTER_LOG -DIPFILTER_LOOKUP -DIPFILTER_SCAN -DIPFILTER_SYNC -DIPFILTER_CKSUM -c ../../ip_proxy.c -o ip_proxy_u.o
"../../netinet/ip_pptp_pxy.c", line 275: cannot do pointer arithmetic on operand of unknown size
cc: acomp failed for ../../ip_proxy.c
*** Error code 2
make: Fatal error: Command failed for target `ip_proxy_u.o'

The type of fin->fin_dp is void *; thus the following patch of
netinet/ip_pptp_pxy.c fixes this:
275c275
< msg = fin->fin_dp + (TCP_OFF(tcp) << 2);
---
> msg = (char *)fin->fin_dp + (TCP_OFF(tcp) << 2);