diff --git a/babel.config.js b/babel.config.js
index c37b9eb4..c9649cff 100644
--- a/babel.config.js
+++ b/babel.config.js
@@ -2,10 +2,6 @@ module.exports = {
   presets: [
     [
       '@babel/preset-env',
-      {
-        useBuiltIns: 'usage',
-        corejs: 3,
-      },
     ],
   ],
   plugins: [
diff --git a/jest.config.js b/jest.config.js
index 481d71dd..d796e238 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -3,4 +3,7 @@ module.exports = {
   roots: [
     '<rootDir>/packages/',
   ],
+  moduleNameMapper: {
+    '\\.(css)$': 'identity-obj-proxy',
+  },
 }
diff --git a/package.json b/package.json
index 8f19cffa..b5e93c7c 100644
--- a/package.json
+++ b/package.json
@@ -39,7 +39,6 @@
     "browser-sync": "^2.26.7",
     "connect-history-api-fallback": "^1.6.0",
     "copy-webpack-plugin": "^5.0.3",
-    "core-js": "^3.1.3",
     "css-loader": "^3.0.0",
     "dart-sass": "^1.21.0",
     "eslint": "^5.16.0",
@@ -53,11 +52,13 @@
     "html-webpack-plugin": "^3.2.0",
     "http-proxy-middleware": "^0.19.1",
     "http-server": "^0.11.1",
+    "identity-obj-proxy": "^3.0.0",
     "imagemin-webpack-plugin": "^2.4.2",
     "jest": "^24.7.1",
     "lerna": "^3.15.0",
     "mini-css-extract-plugin": "^0.7.0",
     "minimist": "^1.2.0",
+    "mutation-observer": "^1.0.3",
     "optimize-css-assets-webpack-plugin": "^5.0.1",
     "ora": "^3.4.0",
     "postcss": "^7.0.17",
diff --git a/packages/tiptap/src/Utils/injectCSS.js b/packages/tiptap/src/Utils/injectCSS.js
index 730d3dc8..79d63363 100644
--- a/packages/tiptap/src/Utils/injectCSS.js
+++ b/packages/tiptap/src/Utils/injectCSS.js
@@ -1,13 +1,15 @@
 export default function (css) {
-  const style = document.createElement('style')
-  style.type = 'text/css'
-  style.textContent = css
-  const { head } = document
-  const { firstChild } = head
+  if (process.env.NODE_ENV !== 'test') {
+    const style = document.createElement('style')
+    style.type = 'text/css'
+    style.textContent = css
+    const { head } = document
+    const { firstChild } = head
 
-  if (firstChild) {
-    head.insertBefore(style, firstChild)
-  } else {
-    head.appendChild(style)
+    if (firstChild) {
+      head.insertBefore(style, firstChild)
+    } else {
+      head.appendChild(style)
+    }
   }
 }
diff --git a/packages/tiptap/test/Editor.spec.js b/packages/tiptap/test/Editor.spec.js
index 974dc76a..ad1c3c57 100644
--- a/packages/tiptap/test/Editor.spec.js
+++ b/packages/tiptap/test/Editor.spec.js
@@ -1,3 +1,5 @@
+// MutationObserver is not supported by JSDom
+import MutationObserver from 'mutation-observer'
 import Editor from '../src/Editor'
 
 import {
@@ -19,6 +21,8 @@ import {
   History,
 } from '../../tiptap-extensions'
 
+global.MutationObserver = MutationObserver
+
 test('create editor', () => {
   const editor = new Editor()
 
diff --git a/yarn.lock b/yarn.lock
index 61a85f68..9d254a0f 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3730,7 +3730,7 @@ core-js@^2.4.0, core-js@^2.6.5:
   resolved "https://registry.yarnpkg.com/core-js/-/core-js-2.6.9.tgz#6b4b214620c834152e179323727fc19741b084f2"
   integrity sha512-HOpZf6eXmnl7la+cUdMnLvUxKNqLUzJvgIziQ0DiF3JwSImNphIqdGqzj6hIKyX04MmV0poclQ7+wjWvxQyR2A==
 
-core-js@^3.0.0, core-js@^3.1.3:
+core-js@^3.0.0:
   version "3.1.3"
   resolved "https://registry.yarnpkg.com/core-js/-/core-js-3.1.3.tgz#95700bca5f248f5f78c0ec63e784eca663ec4138"
   integrity sha512-PWZ+ZfuaKf178BIAg+CRsljwjIMRV8MY00CbZczkR6Zk5LfkSkjGoaab3+bqRQWVITNZxQB7TFYz+CFcyuamvA==
@@ -4530,9 +4530,9 @@ ee-first@1.1.1:
   integrity sha1-WQxhFWsK4vTwJVcyoViyZrxWsh0=
 
 electron-to-chromium@^1.3.150:
-  version "1.3.157"
-  resolved "https://registry.yarnpkg.com/electron-to-chromium/-/electron-to-chromium-1.3.157.tgz#6211d69e8c4ee18df8c84e74e8644bcafc09486c"
-  integrity sha512-vxGi3lOGqlupuogZxJOMfu+Q1vaOlG6XbsblWw8XnUZSr/ptbt3D6jhHT5LJPZuFUpKhbEo1u4QipivSory1Kg==
+  version "1.3.158"
+  resolved "https://registry.yarnpkg.com/electron-to-chromium/-/electron-to-chromium-1.3.158.tgz#5e16909dcfd25ab7cd1665114ee381083a3ee858"
+  integrity sha512-wJsJaWsViNQ129XPGmyO5gGs1jPMHr9vffjHAhUje1xZbEzQcqbENdvfyRD9q8UF0TgFQFCCUbaIpJarFbvsIg==
 
 elliptic@^6.0.0:
   version "6.4.1"
@@ -5777,6 +5777,11 @@ har-validator@~5.1.0:
     ajv "^6.5.5"
     har-schema "^2.0.0"
 
+harmony-reflect@^1.4.6:
+  version "1.6.1"
+  resolved "https://registry.yarnpkg.com/harmony-reflect/-/harmony-reflect-1.6.1.tgz#c108d4f2bb451efef7a37861fdbdae72c9bdefa9"
+  integrity sha512-WJTeyp0JzGtHcuMsi7rw2VwtkvLa+JyfEKJCFyfcS0+CDkjQ5lHPu7zEhFZP+PDSRrEgXa5Ah0l1MbgbE41XjA==
+
 has-ansi@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/has-ansi/-/has-ansi-2.0.0.tgz#34f5049ce1ecdf2b0649af3ef24e45ed35416d91"
@@ -6123,6 +6128,13 @@ icss-utils@^4.0.0, icss-utils@^4.1.1:
   dependencies:
     postcss "^7.0.14"
 
+identity-obj-proxy@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/identity-obj-proxy/-/identity-obj-proxy-3.0.0.tgz#94d2bda96084453ef36fbc5aaec37e0f79f1fc14"
+  integrity sha1-lNK9qWCERT7zb7xarsN+D3nx/BQ=
+  dependencies:
+    harmony-reflect "^1.4.6"
+
 ieee754@^1.1.4:
   version "1.1.13"
   resolved "https://registry.yarnpkg.com/ieee754/-/ieee754-1.1.13.tgz#ec168558e95aa181fd87d37f55c32bbcb6708b84"
@@ -8116,6 +8128,11 @@ multimatch@^2.1.0:
     arrify "^1.0.0"
     minimatch "^3.0.0"
 
+mutation-observer@^1.0.3:
+  version "1.0.3"
+  resolved "https://registry.yarnpkg.com/mutation-observer/-/mutation-observer-1.0.3.tgz#42e9222b101bca82e5ba9d5a7acf4a14c0f263d0"
+  integrity sha512-M/O/4rF2h776hV7qGMZUH3utZLO/jK7p8rnNgGkjKUw8zCGjRQPxB8z6+5l8+VjRUQ3dNYu4vjqXYLr+U8ZVNA==
+
 mute-stream@0.0.7:
   version "0.0.7"
   resolved "https://registry.yarnpkg.com/mute-stream/-/mute-stream-0.0.7.tgz#3075ce93bc21b8fab43e1bc4da7e8115ed1e7bab"