ruby on rails - ERROR bad URI `keep-alive' -

i receive following error in console. searched solution not able find solution.

 completed 200 ok in 201ms (views: 197.1ms | activerecord: 2.1ms)     [2015-07-21 10:47:48] error bad uri `keep-alive'.     [2015-07-21 10:47:48] error bad uri `keep-alive'.         [2015-07-21 10:47:48] error bad uri `keep-alive'. 

and error in screen was:

length required webrick::httpstatus::lengthrequired webrick/1.3.1 (ruby/2.2.1/2015-02-26) @ localhost:3000