Error postgresql90-contrib

[Robert Fitzpatrick]

Getting this error when trying to install the port...

pgbench.o(.text+0x2b0a): In function `main':
: undefined reference to `pthread_create'
gmake[1]: *** [pgbench] Error 1
gmake[1]: Leaving directory 
`/usr/ports/databases/postgresql90-contrib/work/postgresql-9.0.0/contrib/pgbench'
gmake: *** [all] Error 2
*** Error code 2

Would it have anything to do with any of these ports built with threads:

db2# grep -ir thread /var/db/ports
/var/db/ports/perl/options:WITH_THREADS=true
/var/db/ports/python26/options:WITH_THREADS=true
/var/db/ports/apr/options:WITH_THREADS=true
/var/db/ports/apache22/options:WITH_THREADS=true
/var/db/ports/pico-alpine/options:WITH_THREADS=true

Thanks for any help.