Problems with Makefile.local

Hello!
I have some problems with compilation of Asterisk 1.6 on FreeBSD 8.0. I’d like to make Makefile.local for post configuration options. But there are some errors during compilation:

/usr/ports/net/asterisk16/Makefile.local", line 10: warning: duplicate script for target “patch-conf” ignored

My file is like this:

EXT=${ETCDIR}/extensions.conf
SIP=${ETCDIR}/sip.conf
HTP=${ETCDIR}/http.conf
MAN=${ETCDIR}/manager.conf
USR=${ETCDIR}/users.conf

patch-conf:
if [ -f ${SIP} ]; then patch -p0 ${SIP} < ${FILESDIR}/sip.conf-patch;
else ${INSTALL_DATA} ${FILESDIR}/sip.conf ${ETCDIR} ; fi

If somebody knows the solution, please help me.
Thanks in advance

Piotrek