diff --git a/src/node/src/credentials.js b/src/node/src/credentials.js
index dfc1acaf40d7e817688411c3ff866ce42750c0dd..d68d888e6a1d906122a86990fb808a4cd60e78f2 100644
--- a/src/node/src/credentials.js
+++ b/src/node/src/credentials.js
@@ -82,7 +82,7 @@ var _ = require('lodash');
  * @memberof grpc.credentials
  * @alias grpc.credentials.createSsl
  * @kind function
- * @param {Buffer} root_certs The root certificate data
+ * @param {Buffer=} root_certs The root certificate data
  * @param {Buffer=} private_key The client certificate private key, if
  *     applicable
  * @param {Buffer=} cert_chain The client certificate cert chain, if applicable