diff --git a/app/soapbox/hooks/useDimensions.ts b/app/soapbox/hooks/useDimensions.ts
index 2a265c4a6..bf7fc78b8 100644
--- a/app/soapbox/hooks/useDimensions.ts
+++ b/app/soapbox/hooks/useDimensions.ts
@@ -1,4 +1,5 @@
 import { useEffect, useMemo, useState } from 'react';
+import ResizeObserver from 'resize-observer-polyfill';
 
 type UseDimensionsRect = { width: number, height: number };
 type UseDimensionsResult = [Element | null, any, any]
@@ -14,7 +15,7 @@ const useDimensions = (): UseDimensionsResult => {
 
   const observer = useMemo(
     () =>
-      new (window as any).ResizeObserver((entries: any) => {
+      new ResizeObserver((entries: any) => {
         if (entries[0]) {
           const { width, height } = entries[0].contentRect;
           setRect({ width, height });
diff --git a/package.json b/package.json
index d5647cdec..eef743978 100644
--- a/package.json
+++ b/package.json
@@ -181,6 +181,7 @@
     "redux-thunk": "^2.2.0",
     "requestidlecallback": "^0.3.0",
     "reselect": "^4.0.0",
+    "resize-observer-polyfill": "^1.5.1",
     "sass": "^1.20.3",
     "sass-loader": "^13.0.0",
     "semver": "^7.3.2",