diff --git a/internal/jsutil/stream.go b/internal/jsutil/stream.go
index dc8afc92..9c3439ef 100644
--- a/internal/jsutil/stream.go
+++ b/internal/jsutil/stream.go
@@ -111,13 +111,20 @@ func ConvertReadableStreamToReadCloser(stream js.Value) io.ReadCloser {
 //   - ReadableStream: https://developer.mozilla.org/docs/Web/API/ReadableStream
 //   - This implementation is based on: https://deno.land/std@0.139.0/streams/conversion.ts#L230
 type readerToReadableStream struct {
-	reader   io.ReadCloser
-	chunkBuf []byte
+	initialized bool
+	reader      io.ReadCloser
+	chunkBuf    []byte
 }
 
 // Pull implements ReadableStream's pull method.
 //   - https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream/ReadableStream#pull
 func (rs *readerToReadableStream) Pull(controller js.Value) error {
+	if !rs.initialized {
+		ua := NewUint8Array(0)
+		controller.Call("enqueue", ua)
+		rs.initialized = true
+		return nil
+	}
 	n, err := rs.reader.Read(rs.chunkBuf)
 	if n != 0 {
 		ua := NewUint8Array(n)