diff --git a/package-lock.json b/package-lock.json
index 8a1c02f7..86ac9efc 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1308,7 +1308,8 @@
     "core-js": {
       "version": "3.6.5",
       "resolved": "https://registry.npmjs.org/core-js/-/core-js-3.6.5.tgz",
-      "integrity": "sha512-vZVEEwZoIsI+vPEuoF9Iqf5H7/M3eeQqWlQnYa8FSKKePuYTf5MWnxb5SDAzCa60b3JBRS5g9b+Dq7b1y/RCrA=="
+      "integrity": "sha512-vZVEEwZoIsI+vPEuoF9Iqf5H7/M3eeQqWlQnYa8FSKKePuYTf5MWnxb5SDAzCa60b3JBRS5g9b+Dq7b1y/RCrA==",
+      "dev": true
     },
     "core-js-compat": {
       "version": "3.6.5",
@@ -1691,6 +1692,12 @@
         "sourcemap-codec": "^1.4.4"
       }
     },
+    "mdn-polyfills": {
+      "version": "5.20.0",
+      "resolved": "https://registry.npmjs.org/mdn-polyfills/-/mdn-polyfills-5.20.0.tgz",
+      "integrity": "sha512-AbTv1ytcoOUAkxw6u5oo2QPf27kEZgxBAQr49jFb4i2VnTnFGfJbcIQ9UDBOdfNECeXsgkYFwB2BkdeTfOzztw==",
+      "dev": true
+    },
     "mime": {
       "version": "1.6.0",
       "resolved": "https://registry.npmjs.org/mime/-/mime-1.6.0.tgz",
@@ -1881,7 +1888,8 @@
     "regenerator-runtime": {
       "version": "0.13.7",
       "resolved": "https://registry.npmjs.org/regenerator-runtime/-/regenerator-runtime-0.13.7.tgz",
-      "integrity": "sha512-a54FxoJDIr27pgf7IgeQGxmqUNYrcV338lf/6gH456HZ/PhX+5BcwHXG9ajESmwe6WRO0tAzRUrRmNONWgkrew=="
+      "integrity": "sha512-a54FxoJDIr27pgf7IgeQGxmqUNYrcV338lf/6gH456HZ/PhX+5BcwHXG9ajESmwe6WRO0tAzRUrRmNONWgkrew==",
+      "dev": true
     },
     "regenerator-transform": {
       "version": "0.14.5",
diff --git a/package.json b/package.json
index 976d99a1..5f782e52 100644
--- a/package.json
+++ b/package.json
@@ -22,19 +22,20 @@
   },
   "homepage": "https://github.com/bwindels/brawl-chat#readme",
   "devDependencies": {
-    "cheerio": "^1.0.0-rc.3",
-    "finalhandler": "^1.1.1",
-    "impunity": "^0.0.11",
-    "postcss": "^7.0.18",
-    "postcss-import": "^12.0.1",
-    "rollup": "^1.15.6",
-    "serve-static": "^1.13.2",
     "@babel/core": "^7.11.1",
     "@babel/preset-env": "^7.11.0",
     "@rollup/plugin-babel": "^5.1.0",
     "@rollup/plugin-commonjs": "^14.0.0",
     "@rollup/plugin-node-resolve": "^8.4.0",
+    "cheerio": "^1.0.0-rc.3",
     "core-js": "^3.6.5",
-    "regenerator-runtime": "^0.13.7"
+    "finalhandler": "^1.1.1",
+    "impunity": "^0.0.11",
+    "mdn-polyfills": "^5.20.0",
+    "postcss": "^7.0.18",
+    "postcss-import": "^12.0.1",
+    "regenerator-runtime": "^0.13.7",
+    "rollup": "^1.15.6",
+    "serve-static": "^1.13.2"
   }
 }
diff --git a/src/main-legacy.js b/src/main-legacy.js
index dd89783e..06faa75d 100644
--- a/src/main-legacy.js
+++ b/src/main-legacy.js
@@ -18,6 +18,7 @@ limitations under the License.
 // polyfills needed for IE11
 import "core-js/stable";
 import "regenerator-runtime/runtime";
+import "mdn-polyfills/Element.prototype.closest";
 
 import {xhrRequest} from "./matrix/net/request/xhr.js";
 import {SessionContainer} from "./matrix/SessionContainer.js";