diff --git a/cmd/main.go b/cmd/main.go
index f910cc8..cbcdfce 100644
--- a/cmd/main.go
+++ b/cmd/main.go
@@ -251,6 +251,7 @@ func main() {
 			return
 		}
 		w.Header().Add("Content-Type", "application/protobuf")
+		w.Header().Add("Content-Length", strconv.Itoa(len(b)))
 		w.Write(b)
 	})