diff --git a/_posts/2017-02-21-lesson10.md b/_posts/2017-02-21-lesson10.md
index b643df8..5a64fde 100644
--- a/_posts/2017-02-21-lesson10.md
+++ b/_posts/2017-02-21-lesson10.md
@@ -125,7 +125,7 @@ ReactDOM.render(
   handleClickOnLikeButton () {
     this.setState({ count: 0 }) // => this.state.count 还是 undefined
     this.setState({ count: this.state.count + 1}) // => undefined + 1 = NaN
-    this.setState({ count: this.state.count + 2}) // => NaN + 2 = NaN
+    this.setState({ count: this.state.count + 2}) // => undefined + 2 = NaN
   }
 ...
 ```