diff --git a/_examples/hello/Makefile b/_examples/hello/Makefile
index 019492c2..3140ac9c 100644
--- a/_examples/hello/Makefile
+++ b/_examples/hello/Makefile
@@ -4,8 +4,8 @@ dev:
 
 .PHONY: build
 build:
-	go run ../../cmd/workers-assets-gen
-	tinygo build -o ./build/app.wasm -target wasm -no-debug ./...
+	go run ../../cmd/workers-assets-gen -mode=go
+	GOOS=js GOARCH=wasm go build -o ./build/app.wasm .
 
 .PHONY: deploy
 deploy:
diff --git a/_examples/hello/README.md b/_examples/hello/README.md
index f81b3ac7..8133724d 100644
--- a/_examples/hello/README.md
+++ b/_examples/hello/README.md
@@ -15,7 +15,7 @@
 This project requires these tools to be installed globally.
 
 * wrangler
-* tinygo
+* Go
 
 ### Commands
 
diff --git a/internal/jshttp/response.go b/internal/jshttp/response.go
index 93a33d9d..484c83d0 100644
--- a/internal/jshttp/response.go
+++ b/internal/jshttp/response.go
@@ -52,13 +52,14 @@ func newJSResponse(statusCode int, headers http.Header, contentLength int64, bod
 		status == http.StatusNotModified {
 		return jsutil.ResponseClass.New(jsutil.Null, respInit)
 	}
-	var readableStream js.Value
-	if rawBody != nil {
-		readableStream = *rawBody
-	} else if contentLength > 0 {
-		readableStream = jsutil.ConvertReaderToFixedLengthStream(body, contentLength)
-	} else {
-		readableStream = jsutil.ConvertReaderToReadableStream(body)
-	}
+	readableStream := func() js.Value {
+		if rawBody != nil {
+			return *rawBody
+		}
+		if !jsutil.MaybeFixedLengthStreamClass.IsUndefined() && contentLength > 0 {
+			return jsutil.ConvertReaderToFixedLengthStream(body, contentLength)
+		}
+		return jsutil.ConvertReaderToReadableStream(body)
+	}()
 	return jsutil.ResponseClass.New(readableStream, respInit)
 }
diff --git a/internal/jsutil/jsutil.go b/internal/jsutil/jsutil.go
index e5f169ba..17424ef7 100644
--- a/internal/jsutil/jsutil.go
+++ b/internal/jsutil/jsutil.go
@@ -19,9 +19,12 @@ var (
 	Uint8ClampedArrayClass = js.Global().Get("Uint8ClampedArray")
 	ErrorClass             = js.Global().Get("Error")
 	ReadableStreamClass    = js.Global().Get("ReadableStream")
-	FixedLengthStreamClass = js.Global().Get("FixedLengthStream")
 	DateClass              = js.Global().Get("Date")
 	Null                   = js.ValueOf(nil)
+	// MaybeFixedLengthStreamClass is a class for FixedLengthStream.
+	// * This class is only available in Cloudflare Workers.
+	// * If this class is not available, the value will be undefined.
+	MaybeFixedLengthStreamClass = js.Global().Get("FixedLengthStream")
 )
 
 func NewObject() js.Value {
diff --git a/internal/jsutil/stream.go b/internal/jsutil/stream.go
index 9c3439ef..a64492d8 100644
--- a/internal/jsutil/stream.go
+++ b/internal/jsutil/stream.go
@@ -208,11 +208,12 @@ func ConvertReaderToReadableStream(reader io.ReadCloser) js.Value {
 
 // ConvertReaderToFixedLengthStream converts io.ReadCloser to TransformStream.
 func ConvertReaderToFixedLengthStream(rc io.ReadCloser, size int64) js.Value {
-	stream := FixedLengthStreamClass.New(js.ValueOf(size))
+	stream := MaybeFixedLengthStreamClass.New(js.ValueOf(size))
 	go func(writer js.Value) {
 		defer rc.Close()
 
 		chunk := make([]byte, min(size, defaultChunkSize))
+		AwaitPromise(writer.Get("ready"))
 		for {
 			n, err := rc.Read(chunk)
 			if n > 0 {
@@ -221,6 +222,7 @@ func ConvertReaderToFixedLengthStream(rc io.ReadCloser, size int64) js.Value {
 				writer.Call("write", b)
 			}
 			if err != nil {
+				AwaitPromise(writer.Get("ready"))
 				writer.Call("close")
 				return
 			}