diff --git a/src/utils/polyfills.js b/src/utils/polyfills.ts
similarity index 95%
rename from src/utils/polyfills.js
rename to src/utils/polyfills.ts
index 9843e337f..d5b8f9640 100644
--- a/src/utils/polyfills.js
+++ b/src/utils/polyfills.ts
@@ -12,7 +12,7 @@ export default () => {
   const isIE = () => {
     let match;
     const agent = window.navigator.userAgent;
-    const rules = [
+    const rules: [string, RegExp][] = [
       ['edge', /Edge\/([0-9\._]+)/],
       ['ie', /MSIE\s(7\.0)/],
       ['ie', /MSIE\s([0-9\.]+);.*Trident\/[4-7].0/],