Files larger then 2GB with Mac OS X

Hello,

I am trying to write a BigTIFF plugin, and of course the whole point (compared to TIFF) is to write files > 2GB. The plugin works fine on Windows but on Mac (tested with CS3/CS5 32bit/64bit) I always get the error message "Could not write <filename> because the document exceeds the 2.00G limit for saving <plugin name> files". The same error happens with the "SimpleFormat" plugin.

How can I lift this file limit on the Mac? Is there a flag somewhere that I have to set to make this work?

MfG, Thomas.