Can't safely update to xxx (use -F update to force it) ?

[macintoshzoom]

# cd /usr/ports/x11/kde/kdeutils
# make update
..
blah blah
..
Can't safely update to kdeutils-3.5.9p0 (use -F update to force it)
#

How should I do "(use -F update to force it)" from my ports folder, 
there is no "make -f update" command?

Thanks.

Mac