Freebsd410 and postgresql803: src/port compile error

Hi,

I have an error when postgresql 803 compile with flag :

./configure --prefix=/usr/local/postgres --enable-thread-safety

...
gmake[4]: Leaving directory `/var/tmp/postgresql-8.0.3/src/port'
gcc -O2 -Wall -Wmissing-prototypes -Wpointer-arith -fno-strict-aliasing
initdb.o  -L../../../src/port -lpgport -L../../../src/interfaces/libpq
-lpq -L../../../src/port  -Wl,-R/usr/local/postgres/lib -lpgport -lz
-lreadline -lcrypt -lcompat -lm -lutil  -o initdb
../../../src/interfaces/libpq/libpq.so: undefined reference to
`pthread_sigmask'
../../../src/interfaces/libpq/libpq.so: undefined reference to
`pthread_mutex_unlock'
../../../src/interfaces/libpq/libpq.so: undefined reference to
`pthread_mutex_lock'
...

Possible help me ?

Regards
Rmkml