Response.AsAttachment issue: cannot get response if set filename to Chinese text

Prerequisites

• [*] I have written a descriptive issue title
• [*] I have verified that I am running the latest version of Nancy
• I have verified if the problem exist in both DEBUG and RELEASE mode
• [*] I have searched open and closed issues to ensure it has not already been reported

Description

I want to return a file by url like: http://.../getfile?filename=xxxxx my code is like this:

var file = new FileStream(zipPath, FileMode.Open);
string fileName = //set a filename
var response = new StreamResponse(() => file, MimeTypes.GetMimeType(fileName));
return response.AsAttachment(fileName);

when filename is us letter, all ok. when filename include chinese, client cannot get any response, but also no exception.

when I change AsAttachment section to : AsAttachment("fixednamehere.xxx"); it goes well

so I guess is AsAttachment issue.

ps: if only include one or two chinese word, it still ok, client can download file, but got wrong filename. if it include many chinese word, it stuck

System Configuration

• Nancy version:
• Nancy host
  • Nancy.Hosting.Aspnet
  • [*] Nancy.Hosting.Self
  • Nancy.Owin ()
  • Other:
• Other Nancy packages and versions:
• Environment (Operating system, version and so on):
• .NET Framework version:
• Additional information: