diff --git a/packages/@ember/deprecated-features/index.ts b/packages/@ember/deprecated-features/index.ts
index ea8d6037200..354f3956f66 100644
--- a/packages/@ember/deprecated-features/index.ts
+++ b/packages/@ember/deprecated-features/index.ts
@@ -4,7 +4,6 @@
 // not the version that the feature will be removed.
 
 export const SEND_ACTION = !!'3.4.0';
-export const EMBER_EXTEND_PROTOTYPES = !!'3.2.0-beta.5';
 export const ROUTER_EVENTS = !!'4.0.0';
 export const COMPONENT_MANAGER_STRING_LOOKUP = !!'3.8.0';
 export const JQUERY_INTEGRATION = !!'3.9.0';
diff --git a/packages/ember/index.js b/packages/ember/index.js
index 711f183087e..02a8fb88b68 100644
--- a/packages/ember/index.js
+++ b/packages/ember/index.js
@@ -99,7 +99,6 @@ import ApplicationInstance from '@ember/application/instance';
 import Engine from '@ember/engine';
 import EngineInstance from '@ember/engine/instance';
 import { assign } from '@ember/polyfills';
-import { EMBER_EXTEND_PROTOTYPES } from '@ember/deprecated-features';
 
 import {
   templateOnlyComponent,
@@ -151,28 +150,6 @@ Object.defineProperty(Ember, 'lookup', {
   enumerable: false,
 });
 
-if (EMBER_EXTEND_PROTOTYPES) {
-  Object.defineProperty(Ember, 'EXTEND_PROTOTYPES', {
-    enumerable: false,
-    get() {
-      deprecate(
-        'Accessing Ember.EXTEND_PROTOTYPES is deprecated, please migrate to Ember.ENV.EXTEND_PROTOTYPES',
-        false,
-        {
-          id: 'ember-env.old-extend-prototypes',
-          until: '4.0.0',
-          for: 'ember-source',
-          since: {
-            enabled: '3.3.0',
-          },
-        }
-      );
-
-      return ENV.EXTEND_PROTOTYPES;
-    },
-  });
-}
-
 // ****@ember/application****
 Ember.getOwner = getOwner;
 Ember.setOwner = setOwner;
diff --git a/packages/ember/tests/reexports_test.js b/packages/ember/tests/reexports_test.js
index d65c80baa78..b239bfaf707 100644
--- a/packages/ember/tests/reexports_test.js
+++ b/packages/ember/tests/reexports_test.js
@@ -100,16 +100,6 @@ moduleFor(
       assert.notEqual(glimmer.isHTMLSafe, undefined, 'Ember.String.isHTMLSafe is not `undefined`');
     }
 
-    ['@test Ember.EXTEND_PROTOTYPES is present (but deprecated)'](assert) {
-      expectDeprecation(() => {
-        assert.strictEqual(
-          Ember.ENV.EXTEND_PROTOTYPES,
-          Ember.EXTEND_PROTOTYPES,
-          'Ember.EXTEND_PROTOTYPES exists'
-        );
-      }, /EXTEND_PROTOTYPES is deprecated/);
-    }
-
     '@test Ember.FEATURES is exported'(assert) {
       for (let feature in FEATURES) {
         assert.equal(