how do I not strip the binaries?

[Dan Langille]

According to /usr/ports/Mk/bsd.port.mk:

# INSTALL_PROGRAM - A command to install binary executables.  (By
#                    default, also strips them, unless ${STRIP} is
#                    overridden to be the empty string).

For debugging purposes, I don't want the binaries stripped.  I've 
tried defining STRIP in various places (command line, /etc/make.conf) 
but can't stop the stripping:

/usr/bin/install -c -o root -g wheel -s -m 754 bacula-sd 
/usr/local/sbin/bacula-sd

Clues please?  (please cc any replies to me)
-- 
Dan Langille : http://www.langille.org/