diff --git a/src/channel-credentials.ts b/src/channel-credentials.ts
index 75d72802..02a1a399 100644
--- a/src/channel-credentials.ts
+++ b/src/channel-credentials.ts
@@ -6,7 +6,7 @@ import { CallCredentials } from './call-credentials';
 export class ChannelCredentials {
   private constructor() {}
 
-  static createSsl(rootCerts: Buffer, privateKey?: Buffer, certChain?: Buffer) : ChannelCredentials {
+  static createSsl(rootCerts?: Buffer, privateKey?: Buffer, certChain?: Buffer) : ChannelCredentials {
     throw new Error();
   }