diff --git a/ext/call.cc b/ext/call.cc
index 1b2ab21d..c0e2b0f0 100644
--- a/ext/call.cc
+++ b/ext/call.cc
@@ -234,7 +234,9 @@ class SendMetadataOp : public Op {
 
 class SendMessageOp : public Op {
  public:
-  SendMessageOp() { send_message = NULL; }
+  SendMessageOp() {
+    send_message = NULL;
+  }
   ~SendMessageOp() {
     if (send_message != NULL) {
       grpc_byte_buffer_destroy(send_message);
@@ -269,7 +271,6 @@ class SendMessageOp : public Op {
   std::string GetTypeString() const {
     return "send_message";
   }
-
  private:
   grpc_byte_buffer *send_message;
 };
diff --git a/src/credentials.js b/src/credentials.js
index ff10a22e..dcbfac18 100644
--- a/src/credentials.js
+++ b/src/credentials.js
@@ -91,7 +91,7 @@ exports.createSsl = ChannelCredentials.createSsl;
  */
 exports.createFromMetadataGenerator = function(metadata_generator) {
   return CallCredentials.createFromPlugin(function(service_url, callback) {
-    metadata_generator(service_url, function(error, metadata) {
+    metadata_generator({service_url: service_url}, function(error, metadata) {
       var code = grpc.status.OK;
       var message = '';
       if (error) {
@@ -114,7 +114,8 @@ exports.createFromMetadataGenerator = function(metadata_generator) {
  * @return {CallCredentials} The resulting credentials object
  */
 exports.createFromGoogleCredential = function(google_credential) {
-  return exports.createFromMetadataGenerator(function(service_url, callback) {
+  return exports.createFromMetadataGenerator(function(auth_context, callback) {
+    var service_url = auth_context.service_url;
     google_credential.getRequestMetadata(service_url, function(err, header) {
       if (err) {
         callback(err);