在 windows 下执行 compass watch 出错：undefined method 'start'

Question

执行结果如下：

F:\localhost\files\css>compass watch --trace
>>> Compass is watching for changes. Press Ctrl-C to Stop.
[Listen warning]:
  Listen will be polling for changes. Learn more at https://github.com/guard/listen#polling-fallback.
NoMethodError on line ["402"] of D: undefined method `start' for #<Thread:0x0000000297c348 sleep>
  D:/Ruby21-x64/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:402:in `map'
  D:/Ruby21-x64/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:402:in `listen_to'
  D:/Ruby21-x64/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:338:in `watch'
  D:/Ruby21-x64/lib/ruby/gems/2.1.0/gems/compass-1.0.3/lib/compass/sass_compiler.rb:46:in `watch!'
  D:/Ruby21-x64/lib/ruby/gems/2.1.0/gems/compass-1.0.3/lib/compass/commands/watch_project.rb:41:in `perform'
  D:/Ruby21-x64/lib/ruby/gems/2.1.0/gems/compass-1.0.3/lib/compass/commands/base.rb:18:in `execute'
  D:/Ruby21-x64/lib/ruby/gems/2.1.0/gems/compass-1.0.3/lib/compass/commands/project_base.rb:19:in `execute'
  D:/Ruby21-x64/lib/ruby/gems/2.1.0/gems/compass-1.0.3/lib/compass/exec/sub_command_ui.rb:43:in `perform!'
  D:/Ruby21-x64/lib/ruby/gems/2.1.0/gems/compass-1.0.3/lib/compass/exec/sub_command_ui.rb:15:in `run!'
  D:/Ruby21-x64/lib/ruby/gems/2.1.0/gems/compass-1.0.3/bin/compass:30:in `block in <top (required)>'
  D:/Ruby21-x64/lib/ruby/gems/2.1.0/gems/compass-1.0.3/bin/compass:44:in `call'
  D:/Ruby21-x64/lib/ruby/gems/2.1.0/gems/compass-1.0.3/bin/compass:44:in `<top (required)>'
  D:/Ruby21-x64/bin/compass:23:in `load'
  D:/Ruby21-x64/bin/compass:23:in `<main>'