CompressionMethod.Deflate doesn't work on Mono in Windows

The thing is that System.IO.DeflateStream is used. And it uses system implementation if gzip (thats why it doesn't work on Windows at least). One good idea is to use SharpZipLib - it is a pure C# implementation of zip. What do you think, @sta ?

System.DllNotFoundException: MonoPosixHelper
  at (wrapper managed-to-native) System.IO.Compression.DeflateStream:CreateZStream (System.IO.Compression.CompressionMode,bool,System.IO.Compression.DeflateStream/UnmanagedReadOrWrite,intptr)
  at System.IO.Compression.DeflateStream..ctor (System.IO.Stream compressedStream, CompressionMode mode, Boolean leaveOpen, Boolean gzip) [0x00000] in <filename unknown>:0 
  at System.IO.Compression.DeflateStream..ctor (System.IO.Stream compressedStream, CompressionMode mode, Boolean leaveOpen) [0x00000] in <filename unknown>:0 
  at (wrapper remoting-invoke-with-check) System.IO.Compression.DeflateStream:.ctor (System.IO.Stream,System.IO.Compression.CompressionMode,bool)
  at WebSocketSharp.Ext.compress (System.IO.Stream stream) [0x00000] in <filename unknown>:0 
  at WebSocketSharp.Ext.Compress (System.IO.Stream stream, CompressionMethod method) [0x00000] in <filename unknown>:0 
  at WebSocketSharp.WebSocket.send (Opcode opcode, System.IO.Stream stream) [0x00000] in <filename unknown>:0 
UnityEngine.Debug:Log(Object)

Start at WebSocketSharp.Ext.compress and Ext.Compress, where the stack trace shows System.IO.DeflateStream failing under Mono on Windows. Reproduce the Deflate path in the reported Unity environment and review the proposed SharpZipLib option. Done should mean CompressionMethod.Deflate works without the MonoPosixHelper failure.