diff --git a/index.d.ts b/index.d.ts
index 9b77db4752..247ef6e942 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -64,25 +64,25 @@ declare module 'egg' {
      * logger
      * @member {EggLogger}
      */
-    logger: EggLogger;
+    protected logger: EggLogger;
 
     /**
      * The configuration of application
      * @member {EggAppConfig}
      */
-    config: EggAppConfig;
+    protected config: EggAppConfig;
 
     /**
      * The instance of agent
      * @member {Agent}
      */
-    agent: Agent;
+    protected agent: Agent;
 
     /**
      * The instance of app
      * @member {Application}
      */
-    app: Application;
+    protected app: Application;
   }
 
   export type RequestArrayBody = any[];
diff --git a/test/agent.test.js b/test/agent.test.js
index d4b006dc64..aea3ee98b8 100644
--- a/test/agent.test.js
+++ b/test/agent.test.js
@@ -1,8 +1,9 @@
 'use strict';
 
+const assert = require('assert');
 const mock = require('egg-mock');
+const path = require('path');
 const utils = require('./utils');
-const assert = require('assert');
 
 describe('test/agent.test.js', () => {
   afterEach(mock.restore);
@@ -16,6 +17,6 @@ describe('test/agent.test.js', () => {
 
   it('agent logger config should work', () => {
     const fileTransport = app._agent.logger.get('file');
-    assert(fileTransport.options.file === '/tmp/foo/egg-agent.log');
+    assert(fileTransport.options.file === path.join('tmp/foo', 'egg-agent.log'));
   });
 });