diff --git a/index.js b/index.js
index 599b3d9..574cbd0 100644
--- a/index.js
+++ b/index.js
@@ -1,6 +1,6 @@
 import React from "react";
 import ReactDOM from "react-dom";
-import App from "./src/App.jsx";
+import App from "./src/App.tsx";
 
 const root = document.getElementById("root");
 ReactDOM.render(<App />, root);
diff --git a/package.json b/package.json
index 9dad55f..cada33e 100644
--- a/package.json
+++ b/package.json
@@ -10,7 +10,7 @@
     "start": "parcel index.html",
     "build": "parcel build index.html --no-source-maps",
     "prebuild": "yarn run typecheck",
-    "typecheck": "tsc --noEmit",
+    "typecheck": "tsc --noEmit --jsx preserve",
     "lint": "eslint src/*",
     "lint-fix": "eslint src/* --fix"
   },
diff --git a/src/App.jsx b/src/App.tsx
similarity index 97%
rename from src/App.jsx
rename to src/App.tsx
index 576f2b5..39efa03 100644
--- a/src/App.jsx
+++ b/src/App.tsx
@@ -1,7 +1,7 @@
 import React, {Component} from 'react';
 
 import './App.scss';
-import {declineSaimiar} from './saimiar_morphology.ts';
+import {declineSaimiar} from './saimiar_morphology';
 
 const backendUrl = 'https://kucinakobackend.ichigo.everydayimshuflin.com';
 
@@ -14,7 +14,7 @@ function makeRequest(queryString, jsonHandler) {
         });
 }
 
-function renderConlangName(name) {
+function renderConlangName(name: string): string {
     if (name === 'saimiar') {
         return 'Saimiar';
     }
@@ -100,6 +100,10 @@ const Results = (props) => {
     );
 };
 
+interface App {
+    [x: string]: any;
+};
+
 class App extends Component {
     constructor(props) {
         super(props);