How do I increase “ulimit -u” (max user processes)?

Question

I can change all of the usual ulimits via (for instance) ulimit -n 8192 and launchctl limit maxfiles 8192 8192. Somehow, this doesn't seem to work for -u, the maximum number of user processes:

~$ sudo launchctl limit maxproc 8192 8192
~$ sudo launchctl limit maxproc
    maxproc     2048           2048
-- in a new terminal:
~$ ulimit -u
1064

I do get a "failed to fork" every once in a while, and it's quite annoying having to kill a bunch of processes when "kill" can't start :) (i.e. I usually resort to just rebooting the machine).

What's the correct way to change the maximum number of user processes?