anchor.diff:              | None -> Assembly.GetCallingAssembly()
           let url = defaultArg url "http://localhost:9000/"
           let url = if not (url.EndsWith "/") then url + "/" else url
  -        let options = Owin.WarpOptions<_>(?debug = debug, ?rootDir = rootDir, ?scripted = scripted, assembly = assembly)
  +        let options = Owin.WarpOptions<_>(assembly, ?debug = debug, ?rootDir = rootDir, ?scripted = scripted)
           try
               let server = WebApp.Start(url, fun appB ->
                   Owin.UseWarp(appB, sitelet, options)
  
positive.code:                         sitelet)
                  let staticFilesMw =
                      Microsoft.Owin.StaticFiles.StaticFileMiddleware(
                          Func<_,_> siteletMw.Invoke,
                          StaticFileOptions(
                              FileSystem = PhysicalFileSystem(options.RootDir)))
                  staticFilesMw.Invoke(env)
  
      /// Adds the Warp middleware to an Owin.IAppBuilder pipeline.
      [<Extension>]
  
negative.code: module Owin =
  
      /// Warp OWIN middleware options.
      type WarpOptions<'EndPoint when 'EndPoint : equality>(assembly, ?debug, ?rootDir, ?scripted) =
          let debug = defaultArg debug false
          let rootDir = defaultArg rootDir (Directory.GetCurrentDirectory())
          let scripted = defaultArg scripted false
  
          member this.Assembly = assembly
          member this.Debug = debug
          member this.RootDir = rootDir
          member this.Scripted = scripted
  
      /// Warp OWIN middleware.
      /// next: The next OWIN middleware to run, if any.
      /// sitelet: The Warp application to run.
      /// options: Options that instruct the middleware how to run and where to look for files.
      type WarpMiddleware<'EndPoint when 'EndPoint : equality>(next: Owin.AppFunc, sitelet: WarpApplication<'EndPoint>, options: WarpOptions<'EndPoint>) =
          let exec =
              // Compile only when the app starts and not on every request.
              match Compilation.compile options.Assembly with
              | None -> failwith "Failed to compile with WebSharper"
              | Some (asm, refs) ->
                  Compilation.outputFiles options.RootDir refs
                  Compilation.outputFile options.RootDir asm
                  // OWIN middleware form a Russian doll, innermost -> outermost
                  let siteletMw =
                      WebSharper.Owin.SiteletMiddleware(
                          next, 
  