diff --git a/handler.go b/handler.go
index 6043365..5b2c0dc 100644
--- a/handler.go
+++ b/handler.go
@@ -79,16 +79,16 @@ func (h *httpServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		md = metadata.New(len(r.Header) + 8)
 	}
 	for k, v := range r.Header {
-		md.Set(k, strings.Join(v, ", "))
+		md[k] = strings.Join(v, ", ")
 	}
-	md.Set("RemoteAddr", r.RemoteAddr)
-	md.Set("Method", r.Method)
-	md.Set("URL", r.URL.String())
-	md.Set("Proto", r.Proto)
-	md.Set("ContentLength", fmt.Sprintf("%d", r.ContentLength))
-	md.Set("TransferEncoding", strings.Join(r.TransferEncoding, ","))
-	md.Set("Host", r.Host)
-	md.Set("RequestURI", r.RequestURI)
+	md["RemoteAddr"] = r.RemoteAddr
+	md["Method"] = r.Method
+	md["URL"] = r.URL.String()
+	md["Proto"] = r.Proto
+	md["ContentLength"] = fmt.Sprintf("%d", r.ContentLength)
+	md["TransferEncoding"] = strings.Join(r.TransferEncoding, ",")
+	md["Host"] = r.Host
+	md["RequestURI"] = r.RequestURI
 	ctx = metadata.NewIncomingContext(ctx, md)
 
 	defer r.Body.Close()