Indicated that serialize and deserialize are optional
diff --git a/src/node/client.js b/src/node/client.js
index fe7e07e..f913b06 100644
--- a/src/node/client.js
+++ b/src/node/client.js
@@ -45,8 +45,8 @@
* from stream.Duplex.
* @constructor
* @param {grpc.Call} call Call object to proxy
- * @param {function(*):Buffer} serialize Serialization function for requests
- * @param {function(Buffer):*} deserialize Deserialization function for
+ * @param {function(*):Buffer=} serialize Serialization function for requests
+ * @param {function(Buffer):*=} deserialize Deserialization function for
* responses
*/
function GrpcClientStream(call, serialize, deserialize) {
diff --git a/src/node/server.js b/src/node/server.js
index 27a18f5..eca20aa 100644
--- a/src/node/server.js
+++ b/src/node/server.js
@@ -47,8 +47,9 @@
* from stream.Duplex.
* @constructor
* @param {grpc.Call} call Call object to proxy
- * @param {function(*):Buffer} serialize Serialization function for responses
- * @param {function(Buffer):*} deserialize Deserialization function for requests
+ * @param {function(*):Buffer=} serialize Serialization function for responses
+ * @param {function(Buffer):*=} deserialize Deserialization function for
+ * requests
*/
function GrpcServerStream(call, serialize, deserialize) {
Duplex.call(this, {objectMode: true});