diff --git a/server.go b/server.go
index 9379213..2fdb645 100644
--- a/server.go
+++ b/server.go
@@ -18,6 +18,7 @@ func apiV1Main(w http.ResponseWriter, r *http.Request) {
 	logRequestDebug(httputil.DumpRequest(r, true))
 	if checkSignature(r) == false {
 		log.Println("signature of URL incorrect")
+		w.Header().Set("Content-Type", "text/xml; charset=utf-8")
 		w.WriteHeader(http.StatusUnauthorized)
 		fmt.Fprintf(w, "") //empty string
 		return
@@ -60,6 +61,7 @@ func answerWechatPost(w http.ResponseWriter, r *http.Request) {
 	fmt.Printf("decrypt as: %s", d)
 	h := ReadCommonHeader(d)
 	reply, _ := BuildTextMsg(h.MsgType, h.FromUserName)
+	w.Header().Set("Content-Type", "text/xml; charset=utf-8")
 	fmt.Fprint(w, reply)
 	return
 }