diff --git a/examples/r2-image-server/jsutil.go b/examples/r2-image-server/jsutil.go
index fe871c1..d80a77a 100644
--- a/examples/r2-image-server/jsutil.go
+++ b/examples/r2-image-server/jsutil.go
@@ -14,6 +14,7 @@ var (
 	uint8ArrayClass     = global.Get("Uint8Array")
 	errorClass          = global.Get("Error")
 	readableStreamClass = global.Get("ReadableStream")
+	stringClass         = global.Get("String")
 )
 
 func newObject() js.Value {
@@ -29,8 +30,6 @@ func newPromise(fn js.Func) js.Value {
 }
 
 func awaitPromise(promiseVal js.Value) (js.Value, error) {
-	fmt.Println("await promise")
-	fmt.Println(promiseVal.Call("toString").String())
 	resultCh := make(chan js.Value)
 	errCh := make(chan error)
 	var then, catch js.Func
@@ -49,17 +48,15 @@ func awaitPromise(promiseVal js.Value) (js.Value, error) {
 	promiseVal.Call("then", then).Call("catch", catch)
 	select {
 	case result := <-resultCh:
-		fmt.Println("got result of promise")
 		return result, nil
 	case err := <-errCh:
-		fmt.Println("got error of promise")
 		return js.Value{}, err
 	}
 }
 
 // dateToTime converts JavaScript side's Data object into time.Time.
 func dateToTime(v js.Value) (time.Time, error) {
-	milliStr := v.Call("getTime").Call("toString").String()
+	milliStr := stringClass.Invoke(v.Call("getTime")).String()
 	milli, err := strconv.ParseInt(milliStr, 10, 64)
 	if err != nil {
 		return time.Time{}, fmt.Errorf("failed to convert Date to time.Time: %w", err)
diff --git a/examples/r2-image-server/main.go b/examples/r2-image-server/main.go
index d4d70bc..d825e6e 100644
--- a/examples/r2-image-server/main.go
+++ b/examples/r2-image-server/main.go
@@ -5,6 +5,7 @@ import (
 	"io"
 	"log"
 	"net/http"
+	"strings"
 
 	"github.com/syumai/workers"
 )
@@ -21,19 +22,22 @@ func handleErr(w http.ResponseWriter, msg string, err error) {
 // This example is based on implementation in syumai/workers-playground
 // * https://github.com/syumai/workers-playground/blob/e32881648ccc055e3690a0d9c750a834261c333e/r2-image-viewer/src/index.ts#L30
 func handler(w http.ResponseWriter, req *http.Request) {
-	fmt.Println("new R2Bucket")
 	bucket, err := NewR2Bucket(bucketName)
 	if err != nil {
 		handleErr(w, "failed to get R2Bucket\n", err)
 		return
 	}
-	imgPath := req.URL.Path
-	fmt.Println("bucket.get")
+	imgPath := strings.TrimPrefix(req.URL.Path, "/")
 	imgObj, err := bucket.Get(imgPath)
 	if err != nil {
 		handleErr(w, "failed to get R2Object\n", err)
 		return
 	}
+	if imgObj == nil {
+		w.WriteHeader(http.StatusNotFound)
+		w.Write([]byte(fmt.Sprintf("image not found: %s", imgPath)))
+		return
+	}
 	w.Header().Set("Cache-Control", "public, max-age=14400")
 	w.Header().Set("ETag", fmt.Sprintf("W/%s", imgObj.HTTPETag))
 	contentType := "application/octet-stream"
@@ -41,7 +45,6 @@ func handler(w http.ResponseWriter, req *http.Request) {
 		contentType = *imgObj.HTTPMetadata.ContentType
 	}
 	w.Header().Set("Content-Type", contentType)
-	fmt.Println("return result")
 	io.Copy(w, imgObj.Body)
 }
 
diff --git a/examples/r2-image-server/r2object.go b/examples/r2-image-server/r2object.go
index 9403f6d..26e97b1 100644
--- a/examples/r2-image-server/r2object.go
+++ b/examples/r2-image-server/r2object.go
@@ -41,7 +41,6 @@ func (o *R2Object) BodyUsed() (bool, error) {
 // toR2Object converts JavaScript side's R2Object to *R2Object.
 // * https://github.com/cloudflare/workers-types/blob/3012f263fb1239825e5f0061b267c8650d01b717/index.d.ts#L1094
 func toR2Object(v js.Value) (*R2Object, error) {
-	fmt.Println("toR2Object")
 	uploaded, err := dateToTime(v.Get("uploaded"))
 	if err != nil {
 		return nil, fmt.Errorf("error converting uploaded: %w", err)