diff --git a/src/ui/components/ViewWithSize.js b/src/ui/components/ViewWithSize.tsx
similarity index 83%
rename from src/ui/components/ViewWithSize.js
rename to src/ui/components/ViewWithSize.tsx
index 1bb7c89e0..d0b3c2760 100644
--- a/src/ui/components/ViewWithSize.js
+++ b/src/ui/components/ViewWithSize.tsx
@@ -8,24 +8,24 @@
 import {Component} from 'react';
 
 type ViewWithSizeProps = {
-  onSize: (width: number, height: number) => any,
+  onSize: (width: number, height: number) => any;
 };
 
-type ViewWithSizeState = {|
-  width: number,
-  height: number,
-|};
+type ViewWithSizeState = {
+  width: number;
+  height: number;
+};
 
 export default class ViewWithSize extends Component<
   ViewWithSizeProps,
-  ViewWithSizeState,
+  ViewWithSizeState
 > {
   constructor(props: ViewWithSizeProps, context: Object) {
     super(props, context);
     this.state = {height: window.innerHeight, width: window.innerWidth};
   }
 
-  _onResize: Function;
+  _onResize: (event: UIEvent) => void;
 
   componentDidMount() {
     this._onResize = () => {
diff --git a/src/ui/index.js b/src/ui/index.js
index cb56ec2b1..b47d1f101 100644
--- a/src/ui/index.js
+++ b/src/ui/index.js
@@ -113,7 +113,7 @@ export {
 
 // utility elements
 export {default as View} from './components/View.tsx';
-export {default as ViewWithSize} from './components/ViewWithSize.js';
+export {default as ViewWithSize} from './components/ViewWithSize.tsx';
 export {default as Block} from './components/Block.js';
 export {default as FocusableBox} from './components/FocusableBox.js';
 export {default as Sidebar} from './components/Sidebar.tsx';