diff --git a/package.json b/package.json
index f297abd4..07960d72 100644
--- a/package.json
+++ b/package.json
@@ -59,6 +59,11 @@
       "prettier --write"
     ]
   },
+  "dependencies": {
+    "babel-runtime": "^6.26.0",
+    "lodash.debounce": "^4.0.8",
+    "sane-domparser-error": "^0.2.0"
+  },
   "devDependencies": {
     "@commitlint/cli": "^7.0.0",
     "@commitlint/travis-cli": "^7.0.0",
@@ -84,7 +89,6 @@
     "jest-environment-jsdom": "^23.4.0",
     "jsdoc": "^3.5.5",
     "lint-staged": "^10.5.4",
-    "lodash.debounce": "^4.0.8",
     "mini-css-extract-plugin": "^0.4.5",
     "mockdate": "^2.0.2",
     "mol-commitlint-config": "^1.1.0",
@@ -98,12 +102,10 @@
     "rollup-plugin-node-resolve": "^3.3.0",
     "rollup-plugin-sourcemaps": "^0.4.2",
     "rollup-plugin-terser": "^1.0.1",
-    "sane-domparser-error": "^0.2.0",
     "semantic-release": "^15.12.1",
     "terser-webpack-plugin": "^1.1.0",
     "webpack": "^4.16.5",
     "webpack-cli": "^3.1.0",
-    "webpack-dev-server": "^3.1.5",
-    "whatwg-fetch": "^2.0.4"
+    "webpack-dev-server": "^3.1.5"
   }
 }
diff --git a/rollup.config.js b/rollup.config.js
index 37b6fcda..4afa5abc 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -12,23 +12,15 @@ const production = process.env.NODE_ENV === 'production';
 const plugins = [
   sourcemaps(),
   babel({
-    exclude: [
-      '../../node_modules/**',
-      'node_modules/**'
-    ],
+    exclude: ['../../node_modules/**', 'node_modules/**'],
     plugins: ['external-helpers']
   }),
-  resolve({
-    customResolveOptions: {
-      moduleDirectory: [
-        'node_modules',
-        '../../node_modules'
-      ]
-    }
-  }),
   commonjs()
 ];
 
+// NOTE: don't include external dependencies into esm/cjm bundles
+const external = ['babel-runtime/regenerator', 'lodash.debounce', 'sane-domparser-error'];
+
 // NOTE: see https://github.com/rollup/rollup/issues/408 to understand why we silences `THIS_IS_UNDEFINED` warnings
 const onwarn = (warning, warn) => {
   if (warning.code === 'THIS_IS_UNDEFINED') {
@@ -49,6 +41,11 @@ const config = [
     },
     plugins: [
       ...plugins,
+      resolve({
+        customResolveOptions: {
+          moduleDirectory: ['node_modules', '../../node_modules']
+        }
+      }),
       production && terser()
     ]
   },
@@ -60,7 +57,8 @@ const config = [
       file: pkg.module,
       format: 'es'
     },
-    plugins
+    plugins,
+    external
   },
   {
     input: 'src/index.js',
@@ -70,7 +68,8 @@ const config = [
       file: pkg.main,
       format: 'cjs'
     },
-    plugins
+    plugins,
+    external
   }
 ];
 
diff --git a/src/adUnit/helpers/fetch/fetchHtml.js b/src/adUnit/helpers/fetch/fetchHtml.js
index 6180a442..2d07e991 100644
--- a/src/adUnit/helpers/fetch/fetchHtml.js
+++ b/src/adUnit/helpers/fetch/fetchHtml.js
@@ -1,13 +1,7 @@
-// eslint-disable-next-line import/no-unassigned-import
-import 'whatwg-fetch';
-
 const isValidContentType = (contentType) => {
   const normalisedCT = contentType.toLowerCase();
 
-  return [
-    'text/plain',
-    'text/html'
-  ].some((allowedType) => normalisedCT.includes(allowedType));
+  return ['text/plain', 'text/html'].some((allowedType) => normalisedCT.includes(allowedType));
 };
 
 const fetchHtml = async (endpoint) => {
diff --git a/src/vastRequest/helpers/fetch.js b/src/vastRequest/helpers/fetch.js
index c7a37333..17a054f8 100644
--- a/src/vastRequest/helpers/fetch.js
+++ b/src/vastRequest/helpers/fetch.js
@@ -1,6 +1,3 @@
-/* eslint-disable filenames/match-exported, import/no-unassigned-import */
-import 'whatwg-fetch';
-
 const fetch = async (endpoint, options = {}) => {
   const defaults = {
     credentials: 'include'
diff --git a/yarn.lock b/yarn.lock
index 1fc78353..4fb7a2e5 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -10344,10 +10344,6 @@ whatwg-encoding@^1.0.1, whatwg-encoding@^1.0.3:
   dependencies:
     iconv-lite "0.4.24"
 
-whatwg-fetch@^2.0.4:
-  version "2.0.4"
-  resolved "http://registry.npmjs.org/whatwg-fetch/-/whatwg-fetch-2.0.4.tgz#dde6a5df315f9d39991aa17621853d720b85566f"
-
 whatwg-mimetype@^2.1.0, whatwg-mimetype@^2.2.0:
   version "2.3.0"
   resolved "https://registry.yarnpkg.com/whatwg-mimetype/-/whatwg-mimetype-2.3.0.tgz#3d4b1e0312d2079879f826aff18dbeeca5960fbf"