Duplicate application/json in response Content-Type for show/update functions

function(doc,req){
  return {"json": true}
}

curl -v  http://localhost:5984/db/_design/test/_show/json -H "Accept: application/json"
 
* Adding handle: conn: 0x24d8480
* Adding handle: send: 0
* Adding handle: recv: 0
* Curl_addHandleToPipeline: length: 1
* - Conn 0 (0x24d8480) send_pipe: 1, recv_pipe: 0
* About to connect() to localhost port 5984 (#0)
*   Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 5984 (#0)
> GET /db/_design/test/_show/json HTTP/1.1
> User-Agent: curl/7.31.0
> Host: localhost:5984
> Accept: application/json
> 
< HTTP/1.1 200 OK
< Vary: Accept
* Server CouchDB/1.4.0+build.c843cef (Erlang OTP/R16B) is not blacklisted
< Server: CouchDB/1.4.0+build.c843cef (Erlang OTP/R16B)
< Etag: "AW5C2CXR0TS88IZ5N8ZIY995B"
< Date: Wed, 21 Aug 2013 16:06:00 GMT
< Content-Type: application/json, application/json
< Content-Length: 7
< Cache-Control: must-revalidate
< 
"true"
* Connection #0 to host localhost left intact

Content-Type: application/json, application/json