Why cann't I use autoproxy argument in eclipse's ant?

version info in eclipse: Apache Ant(TM) version 1.9.2 compiled on July 8 2013

help info in eclipse: no autoproxy argument

But when I use ant in the command-line,there is autoproxy argument.

help info in command-line(ant 1.9.4): -autoproxy Java1.5+: use the OS proxy settings