diff --git a/examples/multiple-Portal.tsx b/examples/multiple-Portal.tsx
index a1ecbca1..9aa0bc5a 100644
--- a/examples/multiple-Portal.tsx
+++ b/examples/multiple-Portal.tsx
@@ -1,10 +1,12 @@
-import React, { useState } from 'react';
-import ReactDOM from 'react-dom';
+import * as React from 'react';
+import * as ReactDOM from 'react-dom';
 import Dialog from '../src/DialogWrap';
 import Drawer from 'rc-drawer';
 import 'rc-drawer/assets/index.css';
 import 'rc-dialog/assets/index.less';
 
+const { useState } = React;
+
 const Demo = () => {
   const [showDialog, setShowDialog] = useState(false);
   const [showDrawer, setShowDrawer] = useState(false);
diff --git a/package.json b/package.json
index 11e97a87..87f9af1d 100644
--- a/package.json
+++ b/package.json
@@ -49,6 +49,7 @@
     "compile": "rc-tools run compile --babel-runtime",
     "pub": "rc-tools run pub --babel-runtime",
     "lint": "rc-tools run lint --no-js-lint",
+    "lint:ts": "tsc",
     "karma": "rc-test run karma",
     "saucelabs": "rc-test run saucelabs",
     "test": "rc-test run test",
diff --git a/src/Dialog.tsx b/src/Dialog.tsx
index 6e02f6f9..3e32d3bc 100644
--- a/src/Dialog.tsx
+++ b/src/Dialog.tsx
@@ -47,7 +47,11 @@ function offset(el: any) {
 
 // https://github.com/ant-design/ant-design/issues/19340
 // https://github.com/ant-design/ant-design/issues/19332
-let cacheOverflow = {};
+interface ICacheOverflow {
+  overflowX?: string;
+  overflowY?: string;
+}
+let cacheOverflow: ICacheOverflow = {};
 
 export interface IDialogChildProps extends IDialogPropTypes {
   getOpenCount: () => number;
@@ -75,7 +79,6 @@ export default class Dialog extends React.Component<IDialogChildProps, any> {
   private sentinelEnd: HTMLElement;
   private dialogMouseDown: boolean;
   private timeoutId: number;
-  private cacheOverflow: { overflowX: string | null; overflowY: string | null};
 
   constructor(props: IDialogChildProps) {
     super(props);
@@ -383,12 +386,14 @@ export default class Dialog extends React.Component<IDialogChildProps, any> {
       cacheOverflow = {
         overflowX: document.body.style.overflowX,
         overflowY: document.body.style.overflowY,
-      };
+      } as ICacheOverflow;
       document.body.style.overflow = 'hidden';
       switchScrollingEffect();
     } else if (!openCount) {
-      if (cacheOverflow.overflowX !== undefined || cacheOverflow.overflowY !== undefined) {
+      if (cacheOverflow.overflowX !== undefined) {
         document.body.style.overflowX = cacheOverflow.overflowX;
+      }
+      if (cacheOverflow.overflowY !== undefined) {
         document.body.style.overflowY = cacheOverflow.overflowY;
       }
       cacheOverflow = {};