When starting Gant (or Groovy?) with a command line such as: gant -Dfoo=bar create on Windows such that the batch files are used (i.e. no Cygwin or MSYS to provide a Posix shell) then it seems that the startGroovy.bat file is "called" with a parameter -Dfoo=bar but the final java invocation has parameters: -Dfoo bar the = sign is replaced with a space. I am informed that quoting on the command line cures the problem: -D"foo=bar" but I have not tested this, I am just reporting from emails. This definitely seems to be a startGroovy.bat problem though – the Posix shell scripts have no problem.