Cannot increase maxfiles limits on Mac 10.7

I an only set lower values for the launchctl limit maxfiles.

I try launchctl limit maxfiles 2048 2048 and nothing changes:

$ launchctl limit maxfilesmaxfiles    500            500$ launchctl limit maxfiles 2048 2048$ launchctl limit maxfilesmaxfiles    500            500$ launchctl limit maxfiles 1024 1024$ launchctl limit maxfilesmaxfiles    500            500$ launchctl limit maxfiles 499$ launchctl limit maxfilesmaxfiles    499            499

I can only set a lower value. It does not work for higher values.