portinstall breaks with -m "-j 4"

[[LoN]Kamikaze]

When a port installs dependencies prior to building and the -j flag is set for make, portupgrade somehow breaks installing dependencies. If I simply do

# cd /usr/ports/category/port
# make install -j 4

it works fine, but the command

# portinstall category/port -m '-j 4'

does not work if dependencies have to be installed. I have tried to get some insight in this and it seems that the ports depended on simply head to the do-install target, omitting things like do-extract, do-patch and do-build.

The cause is a mystery to me, though.