cluster error

$ node voice_server.js
  info - master started
  info - worker 0 spawned
  info - worker 0 connected
  info - listening for connections
  info - shutting down
warning - kill(SIGKILL)

child_process.js:185
    this.killed = this._internal.kill(constants[sig]);
                               ^
Error: ESRCH, No such process
    at ChildProcess.kill (child_process.js:185:34)
    at /usr/local/lib/node/.npm/cluster/0.2.3/package/lib/master.js:708:17
    at Array.forEach (native)
    at Master.kill (/usr/local/lib/node/.npm/cluster/0.2.3/package/lib/master.js
:707:17)
    at Master.destroy (/usr/local/lib/node/.npm/cluster/0.2.3/package/lib/master
.js:463:8)
    at EventEmitter.<anonymous> (native)
    at EventEmitter.emit (events.js:39:17)
    at SignalWatcher.callback (node.js:230:45)