The generated soure-map looks like this. What's wrong?

/usr/local/lib/node_modules/coffee-script/lib/coffee-script/optparse.js:50

            throw new Error("unrecognized option: " + arg);

                  ^

Error: unrecognized option: --source-map

    at OptionParser.exports.OptionParser.OptionParser.parse (/usr/local/lib/node_modules/coffee-script/lib/coffee-script/optparse.js:50:19)

    at parseOptions (/usr/local/lib/node_modules/coffee-script/lib/coffee-script/command.js:465:29)

    at Object.exports.run (/usr/local/lib/node_modules/coffee-script/lib/coffee-script/command.js:53:5)

    at Object.<anonymous> (/usr/local/lib/node_modules/coffee-script/bin/coffee:7:41)

    at Module._compile (module.js:449:26)

    at Object.Module._extensions..js (module.js:467:10)

    at Module.load (module.js:356:32)

    at Function.Module._load (module.js:312:12)

    at Module.runMain (module.js:492:10)

    at process.startup.processNextTick.process._tickCallback (node.js:244:9)