diff --git a/render/empty.go b/render/empty.go
index 4b1b0751..bfa5a424 100644
--- a/render/empty.go
+++ b/render/empty.go
@@ -19,21 +19,22 @@ func (EmptyRenderFactory) Instance() RenderRecycler {
 }
 
 // Render writes data with custom ContentType.
-func (*EmptyRender) Render(http.ResponseWriter) error {
+func (r *EmptyRender) Render(w http.ResponseWriter) error {
+	r.WriteContentType(w)
 	return fmt.Errorf("empty render,you need register one first")
 }
 
 // WriteContentType writes custom ContentType.
-func (*EmptyRender) WriteContentType(w http.ResponseWriter) {
+func (r *EmptyRender) WriteContentType(w http.ResponseWriter) {
 	// Empty
 }
 
 // Setup set data and opts
-func (*EmptyRender) Setup(data interface{}, opts ...interface{}) {
+func (r *EmptyRender) Setup(data interface{}, opts ...interface{}) {
 	// Empty
 }
 
 // Reset clean data and opts
-func (*EmptyRender) Reset() {
+func (r *EmptyRender) Reset() {
 	// Empty
 }
diff --git a/render/json.go b/render/json.go
index bd572e97..5bf73b93 100644
--- a/render/json.go
+++ b/render/json.go
@@ -168,11 +168,7 @@ func (r *SecureJSON) WriteContentType(w http.ResponseWriter) {
 func (r *JsonpJSON) Setup(data interface{}, opts ...interface{}) {
 	r.Data = data
 	if len(opts) == 1 {
-		if callback, ok := opts[0].(string); ok {
-			r.Callback = callback
-		} else {
-			r.Callback = ""
-		}
+		r.Callback, _ = opts[0].(string)
 	}
 }
 
diff --git a/render/render.go b/render/render.go
index 39a532e7..eb626a83 100644
--- a/render/render.go
+++ b/render/render.go
@@ -22,6 +22,7 @@ const (
 	MsgPackRenderType             // MsgPack Render Type
 	ProtoBufRenderType            // ProtoBuf Render Type
 	EmptyRenderType               // Empty Render Type
+	unknownRenderType             // Unknown Render Type,just used for test
 )
 
 var (
diff --git a/render/render_test.go b/render/render_test.go
index 68c57bd7..edd0817f 100644
--- a/render/render_test.go
+++ b/render/render_test.go
@@ -25,6 +25,23 @@ import (
 // TODO unit tests
 // test errors
 
+func TestRenderEmpty(t *testing.T) {
+	w := httptest.NewRecorder()
+	data := "empty data"
+	r := Default(EmptyRenderType)
+	r.Setup(data)
+	err := r.Render(w)
+	Recycle(EmptyRenderType, r)
+	assert.EqualError(t, err, "empty render,you need register one first")
+}
+
+// test not registered render type
+func TestRenderUnknown(t *testing.T) {
+	r := Default(unknownRenderType)
+	_, ok := r.(*EmptyRender)
+	assert.True(t, ok)
+}
+
 func TestRenderMsgPack(t *testing.T) {
 	w := httptest.NewRecorder()
 	data := map[string]interface{}{