diff --git a/app/javascript/mastodon/components/modal_root.js b/app/javascript/mastodon/components/modal_root.js
index 5d4f4bbe138ecc..c55fa0f74c7c8d 100644
--- a/app/javascript/mastodon/components/modal_root.js
+++ b/app/javascript/mastodon/components/modal_root.js
@@ -1,5 +1,6 @@
 import React from 'react';
 import PropTypes from 'prop-types';
+import 'wicg-inert';
 
 export default class ModalRoot extends React.PureComponent {
 
diff --git a/package.json b/package.json
index 62929ad0a00b4e..1d0c82fa555d01 100644
--- a/package.json
+++ b/package.json
@@ -168,7 +168,8 @@
     "webpack-bundle-analyzer": "^3.6.0",
     "webpack-cli": "^3.3.7",
     "webpack-merge": "^4.2.1",
-    "websocket.js": "^0.1.12"
+    "websocket.js": "^0.1.12",
+    "wicg-inert": "^3.0.0"
   },
   "devDependencies": {
     "babel-eslint": "^10.0.3",
diff --git a/yarn.lock b/yarn.lock
index 35eb1ec33ac14b..8a8f9038dc414e 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -10931,6 +10931,11 @@ which@^2.0.1:
   dependencies:
     isexe "^2.0.0"
 
+wicg-inert@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/wicg-inert/-/wicg-inert-3.0.0.tgz#4f5797172fbf7ff01effd3839b52872e35d3cba2"
+  integrity sha512-sZsYZ8pk8y6CgDLkTxivfhLDBvZuDWTWBawU8OuDdO0Id6AOd1Gqjkvt9g9Ni7rgHIS7UbRvbLSv1z7MSJDYCA==
+
 wide-align@^1.1.0:
   version "1.1.3"
   resolved "https://registry.yarnpkg.com/wide-align/-/wide-align-1.1.3.tgz#ae074e6bdc0c14a431e804e624549c633b000457"