diff --git a/server.go b/server.go
index 3ee94e2..9379213 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.WriteHeader(http.StatusUnauthorized)
 		fmt.Fprintf(w, "") //empty string
 		return
 	}