diff --git a/.gitignore b/.gitignore
index 3557f05..beab98a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -38,3 +38,6 @@ jspm_packages
 .node_repl_history
 
 .DS_Store
+
+# webStorm config file
+.idea
\ No newline at end of file
diff --git a/chapter-02/controlpanel_with_summary/package.json b/chapter-02/controlpanel_with_summary/package.json
index 1557900..dc640c3 100644
--- a/chapter-02/controlpanel_with_summary/package.json
+++ b/chapter-02/controlpanel_with_summary/package.json
@@ -47,6 +47,7 @@
     "whatwg-fetch": "1.0.0"
   },
   "dependencies": {
+    "prop-types": "^15.5.10",
     "react": "^15.4.1",
     "react-dom": "^15.4.1"
   },
@@ -79,4 +80,4 @@
   "eslintConfig": {
     "extends": "react-app"
   }
-}
\ No newline at end of file
+}
diff --git a/chapter-02/controlpanel_with_summary/src/Counter.js b/chapter-02/controlpanel_with_summary/src/Counter.js
index 63726fa..b782a75 100644
--- a/chapter-02/controlpanel_with_summary/src/Counter.js
+++ b/chapter-02/controlpanel_with_summary/src/Counter.js
@@ -1,4 +1,5 @@
-import React, { Component, PropTypes } from 'react';
+import React, { Component } from 'react';
+import PropTypes from 'prop-types';
 
 const buttonStyle = {
   margin: '10px'