fs.watch(): EINVAL on Windows watching a root file

node.js: 4.2.1
OS: Win10

have a file test.txt directly on C:
try to watch it: fs.watch("C:\\test.txt")

> fs.watch("C:\\test.txt")
Error: watch C:\test.txt EINVAL
    at exports._errnoException (util.js:874:11)
    at FSWatcher.start (fs.js:1239:19)
    at Object.fs.watch (fs.js:1267:11)
    at repl:1:4
    at REPLServer.defaultEval (repl.js:164:27)
    at bound (domain.js:280:14)
    at REPLServer.runBound [as eval] (domain.js:293:12)
    at REPLServer.<anonymous> (repl.js:393:12)
    at emitOne (events.js:82:20)
    at REPLServer.emit (events.js:169:7)