diff --git a/.github/workflows/size.yaml b/.github/workflows/size.yaml
index 5c2d03985b..d9aa4474dc 100644
--- a/.github/workflows/size.yaml
+++ b/.github/workflows/size.yaml
@@ -14,4 +14,4 @@ jobs:
       - uses: preactjs/compressed-size-action@v1
         with:
           repo-token: '${{ secrets.GITHUB_TOKEN }}'
-          pattern: './{dist,es,lib}/*.js'
+          pattern: './{dist,es,lib}/*.{js,mjs}'
diff --git a/index.d.ts b/index.d.ts
index b00c6f0885..4a4d4e0ad5 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,5 +1,3 @@
-/// <reference types="symbol-observable" />
-
 /**
  * An *action* is a plain object that represents an intention to change the
  * state. Actions are the only way to get data into the store. Any data,
@@ -224,6 +222,12 @@ export interface Unsubscribe {
   (): void
 }
 
+declare global {
+  interface SymbolConstructor {
+    readonly observable: symbol
+  }
+}
+
 /**
  * A minimal observable of state changes.
  * For more information, see the observable proposal:
diff --git a/package-lock.json b/package-lock.json
index e4462bfb49..8670b47592 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -7073,7 +7073,8 @@
     "js-tokens": {
       "version": "3.0.2",
       "resolved": "https://registry.npmjs.org/js-tokens/-/js-tokens-3.0.2.tgz",
-      "integrity": "sha1-mGbfOVECEw449/mWvOtlRDIJwls="
+      "integrity": "sha1-mGbfOVECEw449/mWvOtlRDIJwls=",
+      "dev": true
     },
     "js-yaml": {
       "version": "3.14.1",
@@ -7296,6 +7297,7 @@
       "version": "1.4.0",
       "resolved": "https://registry.npmjs.org/loose-envify/-/loose-envify-1.4.0.tgz",
       "integrity": "sha512-lyuxPGr/Wfhrlem2CL/UcnUc1zcqKAImBDzukY7Y5F/yQiNdko6+fRLevlw1HgMySw7f611UIY408EtxRSoK3Q==",
+      "dev": true,
       "requires": {
         "js-tokens": "^3.0.0 || ^4.0.0"
       }
@@ -9508,11 +9510,6 @@
         }
       }
     },
-    "symbol-observable": {
-      "version": "2.0.3",
-      "resolved": "https://registry.npmjs.org/symbol-observable/-/symbol-observable-2.0.3.tgz",
-      "integrity": "sha512-sQV7phh2WCYAn81oAkakC5qjq2Ml0g8ozqz03wOGnx9dDlG1de6yrF+0RAzSJD8fPUow3PTSMf2SAbOGxb93BA=="
-    },
     "symbol-tree": {
       "version": "3.2.4",
       "resolved": "https://registry.npmjs.org/symbol-tree/-/symbol-tree-3.2.4.tgz",
diff --git a/package.json b/package.json
index a57914cae3..59ec76e0d3 100644
--- a/package.json
+++ b/package.json
@@ -49,8 +49,6 @@
     "examples:test": "cross-env CI=true babel-node examples/testAll.js"
   },
   "dependencies": {
-    "loose-envify": "^1.4.0",
-    "symbol-observable": "^2.0.3",
     "@babel/runtime": "^7.9.2"
   },
   "devDependencies": {
@@ -102,11 +100,6 @@
       ]
     }
   ],
-  "browserify": {
-    "transform": [
-      "loose-envify"
-    ]
-  },
   "jest": {
     "testRegex": "(/test/.*\\.spec\\.[tj]s)$",
     "coverageProvider": "v8"
diff --git a/src/createStore.js b/src/createStore.js
index 5326a52ff8..5e64e323d1 100644
--- a/src/createStore.js
+++ b/src/createStore.js
@@ -1,4 +1,4 @@
-import $$observable from 'symbol-observable'
+import $$observable from './utils/symbol-observable'
 
 import ActionTypes from './utils/actionTypes'
 import isPlainObject from './utils/isPlainObject'
diff --git a/src/utils/symbol-observable.js b/src/utils/symbol-observable.js
new file mode 100644
index 0000000000..0fb198c986
--- /dev/null
+++ b/src/utils/symbol-observable.js
@@ -0,0 +1,3 @@
+// Inlined version of the `symbol-observable` polyfill
+export default (() =>
+  (typeof Symbol === 'function' && Symbol.observable) || '@@observable')()
diff --git a/test/createStore.spec.js b/test/createStore.spec.js
index dcbf65cf3e..5ed9246bdc 100644
--- a/test/createStore.spec.js
+++ b/test/createStore.spec.js
@@ -11,12 +11,15 @@ import {
 import * as reducers from './helpers/reducers'
 import { from } from 'rxjs'
 import { map } from 'rxjs/operators'
-import $$observable from 'symbol-observable'
+import $$observable from '../src/utils/symbol-observable'
 
 describe('createStore', () => {
   it('exposes the public API', () => {
     const store = createStore(combineReducers(reducers))
-    const methods = Object.keys(store)
+
+    // Since switching to internal Symbol.observable impl, it will show up as a key in node env
+    // So we filter it out
+    const methods = Object.keys(store).filter((key) => key !== $$observable)
 
     expect(methods.length).toBe(4)
     expect(methods).toContain('subscribe')
diff --git a/test/typescript/store.ts b/test/typescript/store.ts
index 685bfbf1b6..2d66396887 100644
--- a/test/typescript/store.ts
+++ b/test/typescript/store.ts
@@ -9,7 +9,8 @@ import {
   Unsubscribe,
   Observer,
 } from 'redux'
-import 'symbol-observable'
+// @ts-ignore
+import $$observable from '../src/utils/symbol-observable'
 
 type BrandedString = string & { _brand: 'type' }
 const brandedString = 'a string' as BrandedString