diff --git a/ext/call_credentials.h b/ext/call_credentials.h
index 1cd8d8dd..a9bfe30f 100644
--- a/ext/call_credentials.h
+++ b/ext/call_credentials.h
@@ -84,7 +84,7 @@ typedef struct plugin_callback_data {
   void *user_data;
 } plugin_callback_data;
 
-void plugin_get_metadata(void *state, const char *service_url,
+void plugin_get_metadata(void *state, grpc_auth_metadata_context context,
                          grpc_credentials_plugin_metadata_cb cb,
                          void *user_data);