diff --git a/README.md b/README.md
index 693368938..1fc84de6a 100644
--- a/README.md
+++ b/README.md
@@ -12,6 +12,7 @@
 ![JS gzip size](http://img.badgesize.io/https://unpkg.com/element-ui/lib/index.js?compression=gzip&label=gzip%20size:%20JS)
 ![CSS gzip size](http://img.badgesize.io/https://unpkg.com/element-ui/lib/theme-default/index.css?compression=gzip&label=gzip%20size:%20CSS)
 [![Join the chat at https://gitter.im/ElemeFE/element](https://badges.gitter.im/ElemeFE/element.svg)](https://gitter.im/ElemeFE/element?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+[![Join the chat at https://gitter.im/element-en/Lobby](https://badges.gitter.im/element-en/Lobby.svg)](https://gitter.im/element-en/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 [![OpenCollective](https://opencollective.com/element/backers/badge.svg)](#backers) 
 [![OpenCollective](https://opencollective.com/element/sponsors/badge.svg)](#sponsors)
 
diff --git a/examples/docs/zh-CN/tree.md b/examples/docs/zh-CN/tree.md
index f5d3c3f92..c34df6034 100644
--- a/examples/docs/zh-CN/tree.md
+++ b/examples/docs/zh-CN/tree.md
@@ -698,7 +698,7 @@
 
 ### 手风琴模式
 
-每次只打开一个同级树节点展开
+对于同一级的节点，每次只能展开一个
 
 ::: demo
 ```html
diff --git a/packages/tree/src/model/tree-store.js b/packages/tree/src/model/tree-store.js
index 981af1f35..7e60e5be9 100644
--- a/packages/tree/src/model/tree-store.js
+++ b/packages/tree/src/model/tree-store.js
@@ -132,7 +132,7 @@ export default class TreeStore {
     if (!key || !node || !node.data) return;
 
     const nodeKey = node.key;
-    if (nodeKey) this.nodesMap[node.key] = node;
+    if (nodeKey !== undefined) this.nodesMap[node.key] = node;
   }
 
   deregisterNode(node) {
diff --git a/packages/upload/src/ajax.js b/packages/upload/src/ajax.js
index f5bfa14a0..de05bdb7c 100644
--- a/packages/upload/src/ajax.js
+++ b/packages/upload/src/ajax.js
@@ -5,7 +5,7 @@ function getError(action, option, xhr) {
   } else if (xhr.responseText) {
     msg = `${xhr.status} ${xhr.responseText}`;
   } else {
-    msg = `fail to post ${action} ${xhr.status}'`;
+    msg = `fail to post ${action} ${xhr.status}`;
   }
 
   const err = new Error(msg);