diff --git a/addon/-private/system/model/internal-model.js b/addon/-private/system/model/internal-model.js
index d8f99b67a17..936a6385402 100644
--- a/addon/-private/system/model/internal-model.js
+++ b/addon/-private/system/model/internal-model.js
@@ -1,7 +1,6 @@
-import { assign, merge } from '@ember/polyfills';
 import { A } from '@ember/array';
 import { set, get } from '@ember/object';
-import { copy } from '@ember/object/internals';
+import { assign } from '@ember/polyfills';
 import EmberError from '@ember/error';
 import { isEqual } from '@ember/utils';
 import { setOwner } from '@ember/application';
@@ -24,8 +23,6 @@ import {
   HasManyReference
 } from "../references";
 
-const emberAssign = assign || merge;
-
 /*
   The TransitionChainMap caches the `state.enters`, `state.setups`, and final state reached
   when transitioning from one state to another, so that future transitions can replay the
@@ -636,7 +633,7 @@ export default class InternalModel {
       changedKeys = this._changedKeys(data.attributes);
     }
 
-    emberAssign(this._data, data.attributes);
+    assign(this._data, data.attributes);
     this.pushedData();
 
     if (this.hasRecord) {
@@ -809,7 +806,7 @@ export default class InternalModel {
     let oldData = this._data;
     let currentData = this._attributes;
     let inFlightData = this._inFlightAttributes;
-    let newData = emberAssign(copy(inFlightData), currentData);
+    let newData = assign({}, inFlightData, currentData);
     let diffData = Object.create(null);
     let newDataKeys = Object.keys(newData);
 
@@ -1173,9 +1170,9 @@ export default class InternalModel {
     this.didCleanError();
     let changedKeys = this._changedKeys(data);
 
-    emberAssign(this._data, this._inFlightAttributes);
+    assign(this._data, this._inFlightAttributes);
     if (data) {
-      emberAssign(this._data, data);
+      assign(this._data, data);
     }
 
     this._inFlightAttributes = null;
@@ -1303,8 +1300,8 @@ export default class InternalModel {
         attrs= this._attributes;
       }
 
-      original = emberAssign(Object.create(null), this._data);
-      original = emberAssign(original, this._inFlightAttributes);
+      original = Object.create(null);
+      assign(original, this._data, this._inFlightAttributes);
 
       for (i = 0; i < length; i++) {
         key = keys[i];
diff --git a/addon/-private/system/snapshot.js b/addon/-private/system/snapshot.js
index 8d9d30f1f61..369e868a3f1 100644
--- a/addon/-private/system/snapshot.js
+++ b/addon/-private/system/snapshot.js
@@ -1,12 +1,10 @@
 /**
   @module ember-data
 */
-
-import { copy } from '@ember/object/internals';
-
 import { inspect } from '@ember/debug';
 import EmberError from '@ember/error';
 import { get } from '@ember/object';
+import { assign } from '@ember/polyfills';
 
 /**
   @class Snapshot
@@ -150,7 +148,7 @@ export default class Snapshot {
    @return {Object} All attributes of the current snapshot
    */
   attributes() {
-    return copy(this._attributes);
+    return assign({}, this._attributes);
   }
 
   /**
@@ -173,7 +171,7 @@ export default class Snapshot {
 
     for (let i=0, length = changedAttributeKeys.length; i < length; i++) {
       let key = changedAttributeKeys[i];
-      changedAttributes[key] = copy(this._changedAttributes[key]);
+      changedAttributes[key] = this._changedAttributes[key].slice();
     }
 
     return changedAttributes;
diff --git a/addon/-private/system/store.js b/addon/-private/system/store.js
index 44ec7050193..f57a811e28c 100644
--- a/addon/-private/system/store.js
+++ b/addon/-private/system/store.js
@@ -3,12 +3,11 @@
 */
 
 import { A } from '@ember/array';
-
-import { copy } from '@ember/object/internals';
 import EmberError from '@ember/error';
 import MapWithDefault from './map-with-default';
 import { run as emberRun } from '@ember/runloop';
 import { set, get, computed } from '@ember/object';
+import { assign } from '@ember/polyfills';
 import { default as RSVP, Promise } from 'rsvp';
 import Service from '@ember/service';
 import { typeOf, isPresent, isNone } from '@ember/utils';
@@ -321,7 +320,7 @@ Store = Service.extend({
     return emberRun.join(() => {
       return this._backburner.join(() => {
         let normalizedModelName = normalizeModelName(modelName);
-        let properties = copy(inputProperties) || Object.create(null);
+        let properties = assign({}, inputProperties);
 
         // If the passed properties do not include a primary key,
         // give the adapter an opportunity to generate one. Typically,
diff --git a/tests/helpers/deep-copy.js b/tests/helpers/deep-copy.js
new file mode 100644
index 00000000000..143c31d3dbc
--- /dev/null
+++ b/tests/helpers/deep-copy.js
@@ -0,0 +1,54 @@
+/* global WeakMap */
+export default function deepCopy(obj) {
+  return _deepCopy(obj, new WeakMap());
+}
+
+function isPrimitive(value) {
+  return typeof value !== 'object' || value === null;
+}
+
+function _deepCopy(oldObject, seen) {
+  if (Array.isArray(oldObject)) {
+    return copyArray(oldObject, seen);
+  } else if (!isPrimitive(oldObject)) {
+    return copyObject(oldObject, seen);
+  } else {
+    return oldObject;
+  }
+}
+
+function copyObject(oldObject, seen) {
+  let newObject = {};
+
+  Object.keys(oldObject).forEach(key => {
+    let value = oldObject[key];
+    let newValue = isPrimitive(value) ? value : seen.get(value);
+
+    if (value && newValue === undefined) {
+      newValue = newObject[key] = _deepCopy(value, seen);
+      seen.set(value, newValue);
+    }
+
+    newObject[key] = newValue;
+  });
+
+  return newObject;
+}
+
+function copyArray(oldArray, seen) {
+  let newArray = [];
+
+  for (let i = 0; i < oldArray.length; i++) {
+    let value = oldArray[i];
+    let newValue = isPrimitive(value) ? value : seen.get(value);
+
+    if (value && newValue === undefined) {
+      newValue = newArray[i] = _deepCopy(value, seen);
+      seen.set(value, newValue);
+    }
+
+    newArray[i] = newValue;
+  }
+
+  return newArray;
+}
diff --git a/tests/integration/adapter/build-url-mixin-test.js b/tests/integration/adapter/build-url-mixin-test.js
index a2cacd1da63..e97535f32b1 100644
--- a/tests/integration/adapter/build-url-mixin-test.js
+++ b/tests/integration/adapter/build-url-mixin-test.js
@@ -1,8 +1,8 @@
 import { decamelize, underscore } from '@ember/string';
-import { copy } from '@ember/object/internals';
 import RSVP from 'rsvp';
 import { run } from '@ember/runloop';
 import setupStore from 'dummy/tests/helpers/store';
+import deepCopy from 'dummy/tests/helpers/deep-copy';
 import { pluralize } from 'ember-inflector';
 
 import { module, test } from 'qunit';
@@ -46,7 +46,7 @@ function ajaxResponse(value) {
   adapter.ajax = function(url, verb, hash) {
     passedUrl = url;
 
-    return run(RSVP, 'resolve', copy(value, true));
+    return run(RSVP, 'resolve', deepCopy(value));
   };
 }
 
diff --git a/tests/integration/adapter/rest-adapter-test.js b/tests/integration/adapter/rest-adapter-test.js
index e5ac658334b..cdb94a18b74 100644
--- a/tests/integration/adapter/rest-adapter-test.js
+++ b/tests/integration/adapter/rest-adapter-test.js
@@ -1,11 +1,10 @@
 import { underscore } from '@ember/string';
-import { copy } from '@ember/object/internals';
 import RSVP, { resolve, reject } from 'rsvp';
 import { run } from '@ember/runloop';
 import { get } from '@ember/object';
 import setupStore from 'dummy/tests/helpers/store';
 import { singularize } from 'ember-inflector';
-
+import deepCopy from 'dummy/tests/helpers/deep-copy';
 import testInDebug from 'dummy/tests/helpers/test-in-debug';
 import { module, test } from 'qunit';
 
@@ -56,7 +55,7 @@ function ajaxResponse(value) {
     passedVerb = verb;
     passedHash = hash;
 
-    return run(RSVP, 'resolve', copy(value, true));
+    return run(RSVP, 'resolve', deepCopy(value));
   };
 }
 
diff --git a/tests/integration/records/rematerialize-test.js b/tests/integration/records/rematerialize-test.js
index 76dfdaba91c..19e72905cb6 100644
--- a/tests/integration/records/rematerialize-test.js
+++ b/tests/integration/records/rematerialize-test.js
@@ -1,12 +1,11 @@
 /*eslint no-unused-vars: ["error", { "varsIgnorePattern": "(adam|bob|dudu)" }]*/
 
 import { run } from '@ember/runloop';
-import Ember from 'ember';
 import setupStore from 'dummy/tests/helpers/store';
+import deepCopy from 'dummy/tests/helpers/deep-copy';
 import { module, test } from 'qunit';
 import DS from 'ember-data';
 
-const { copy } = Ember;
 const { attr, belongsTo, hasMany, Model } = DS;
 
 let env;
@@ -173,9 +172,9 @@ test("an async has many relationship to an unloaded record can restore that reco
 
     let data;
     if (param === '1') {
-      data = copy(BOAT_ONE, true);
+      data = deepCopy(BOAT_ONE);
     } else if (param === '1') {
-      data = copy(BOAT_TWO, true);
+      data = deepCopy(BOAT_TWO);
     } else {
       throw new Error(`404: no such boat with id=${param}`);
     }
@@ -208,8 +207,8 @@ test("an async has many relationship to an unloaded record can restore that reco
   run(() => {
     env.store.push({
       data: [
-        copy(BOAT_ONE, true),
-        copy(BOAT_TWO, true)
+        deepCopy(BOAT_ONE),
+        deepCopy(BOAT_TWO)
       ]
     });
   });
diff --git a/tests/integration/relationships/json-api-links-test.js b/tests/integration/relationships/json-api-links-test.js
index 7c094e7b4c3..d92ea3d1879 100644
--- a/tests/integration/relationships/json-api-links-test.js
+++ b/tests/integration/relationships/json-api-links-test.js
@@ -1,6 +1,5 @@
 import { run } from '@ember/runloop';
 import { get } from '@ember/object';
-import Ember from 'ember';
 import { resolve } from 'rsvp';
 import setupStore from 'dummy/tests/helpers/store';
 import {
@@ -9,8 +8,8 @@ import {
 import { module, test } from 'qunit';
 import DS from 'ember-data';
 import JSONAPIAdapter from "ember-data/adapters/json-api";
+import deepCopy from 'dummy/tests/helpers/deep-copy';
 
-const { copy } = Ember;
 const { Model, attr, hasMany, belongsTo } = DS;
 
 let env, User, Organisation;
@@ -711,11 +710,11 @@ function shouldFetchLinkTests(description, payloads) {
         link === payloads.user.data.relationships.pets.links.related,
         'We fetched the appropriate link'
       );
-      return resolve(copy(payloads.pets, true));
+      return resolve(deepCopy(payloads.pets));
     };
 
     // setup user
-    let user = run(() => store.push(copy(payloads.user, true)));
+    let user = run(() => store.push(deepCopy(payloads.user)));
     let pets = run(() => user.get('pets'));
 
     assert.ok(!!pets, 'We found our pets');
@@ -748,11 +747,11 @@ function shouldFetchLinkTests(description, payloads) {
           'We fetched the appropriate link'
         );
       }
-      return resolve(copy(payloads.pets, true));
+      return resolve(deepCopy(payloads.pets));
     };
 
     // setup user
-    let user = run(() => store.push(copy(payloads.user, true)));
+    let user = run(() => store.push(deepCopy(payloads.user)));
     let pets = run(() => user.get('pets'));
 
     assert.ok(!!pets, 'We found our pets');
@@ -790,11 +789,11 @@ function shouldFetchLinkTests(description, payloads) {
           'We fetched the appropriate link'
         );
       }
-      return resolve(copy(payloads.home, true));
+      return resolve(deepCopy(payloads.home));
     };
 
     // setup user
-    let user = run(() => store.push(copy(payloads.user, true)));
+    let user = run(() => store.push(deepCopy(payloads.user)));
     let home = run(() => user.get('home'));
 
     if (homeRelWasEmpty) {
@@ -826,11 +825,11 @@ function shouldFetchLinkTests(description, payloads) {
         link === payloads.user.data.relationships.home.links.related,
         'We fetched the appropriate link'
       );
-      return resolve(copy(payloads.home, true));
+      return resolve(deepCopy(payloads.home));
     };
 
     // setup user
-    let user = run(() => store.push(copy(payloads.user, true)));
+    let user = run(() => store.push(deepCopy(payloads.user)));
     let home = run(() => user.get('home'));
 
     assert.ok(!!home, 'We found our home');
@@ -996,12 +995,12 @@ function shouldReloadWithLinkTests(description, payloads) {
         link === payloads.user.data.relationships.pets.links.related,
         'We fetched the appropriate link'
       );
-      return resolve(copy(payloads.pets, true));
+      return resolve(deepCopy(payloads.pets));
     };
 
     // setup user and pets
-    let user = run(() => store.push(copy(payloads.user, true)));
-    run(() => store.push(copy(payloads.pets, true)));
+    let user = run(() => store.push(deepCopy(payloads.user)));
+    run(() => store.push(deepCopy(payloads.pets)));
     let pets = run(() => user.get('pets'));
 
     assert.ok(!!pets, 'We found our pets');
@@ -1024,12 +1023,12 @@ function shouldReloadWithLinkTests(description, payloads) {
         link === payloads.user.data.relationships.pets.links.related,
         'We fetched the appropriate link'
       );
-      return resolve(copy(payloads.pets, true));
+      return resolve(deepCopy(payloads.pets));
     };
 
     // setup user and pets
-    let user = run(() => store.push(copy(payloads.user, true)));
-    run(() => store.push(copy(payloads.pets, true)));
+    let user = run(() => store.push(deepCopy(payloads.user)));
+    run(() => store.push(deepCopy(payloads.pets)));
     let pets = run(() => user.get('pets'));
 
     assert.ok(!!pets, 'We found our pets');
@@ -1053,12 +1052,12 @@ function shouldReloadWithLinkTests(description, payloads) {
         link === payloads.user.data.relationships.home.links.related,
         'We fetched the appropriate link'
       );
-      return resolve(copy(payloads.home, true));
+      return resolve(deepCopy(payloads.home));
     };
 
     // setup user and home
-    let user = run(() => store.push(copy(payloads.user, true)));
-    run(() => store.push(copy(payloads.home, true)));
+    let user = run(() => store.push(deepCopy(payloads.user)));
+    run(() => store.push(deepCopy(payloads.home)));
     let home = run(() => user.get('home'));
 
     assert.ok(!!home, 'We found our home');
@@ -1081,12 +1080,12 @@ function shouldReloadWithLinkTests(description, payloads) {
         link === payloads.user.data.relationships.home.links.related,
         'We fetched the appropriate link'
       );
-      return resolve(copy(payloads.home, true));
+      return resolve(deepCopy(payloads.home));
     };
 
     // setup user
-    let user = run(() => store.push(copy(payloads.user, true)));
-    run(() => store.push(copy(payloads.home, true)));
+    let user = run(() => store.push(deepCopy(payloads.user)));
+    run(() => store.push(deepCopy(payloads.home)));
     let home;
     run(() => user.get('home').then(h => home = h));
 
@@ -1908,8 +1907,8 @@ test('We should not fetch a hasMany relationship with links that we know is empt
   };
 
   // setup users
-  let user1 = run(() => store.push(copy(user1Payload, true)));
-  let user2 = run(() => store.push(copy(user2Payload, true)));
+  let user1 = run(() => store.push(deepCopy(user1Payload)));
+  let user2 = run(() => store.push(deepCopy(user2Payload)));
 
   // should not fire a request
   requestedUser = null;
diff --git a/tests/integration/store-test.js b/tests/integration/store-test.js
index 4c787f80aad..489b0622520 100644
--- a/tests/integration/store-test.js
+++ b/tests/integration/store-test.js
@@ -1,4 +1,3 @@
-import { copy } from '@ember/object/internals';
 import RSVP, {
   Promise as EmberPromise,
   resolve
@@ -7,6 +6,7 @@ import { run, next } from '@ember/runloop';
 import setupStore from 'dummy/tests/helpers/store';
 
 import testInDebug from 'dummy/tests/helpers/test-in-debug';
+import deepCopy from 'dummy/tests/helpers/deep-copy';
 import { module, test } from 'qunit';
 
 import DS from 'ember-data';
@@ -211,7 +211,7 @@ test("destroying the store correctly cleans everything up", function(assert) {
 
 function ajaxResponse(value) {
   env.adapter.ajax = function(url, verb, hash) {
-    return run(RSVP, 'resolve', copy(value, true));
+    return run(RSVP, 'resolve', deepCopy(value));
   };
 }
 
diff --git a/tests/unit/system/relationships/polymorphic-relationship-payloads-test.js b/tests/unit/system/relationships/polymorphic-relationship-payloads-test.js
index f1a62e54ae3..f14a2e2ec18 100644
--- a/tests/unit/system/relationships/polymorphic-relationship-payloads-test.js
+++ b/tests/unit/system/relationships/polymorphic-relationship-payloads-test.js
@@ -1,8 +1,8 @@
 import { run } from '@ember/runloop';
-import { copy } from '@ember/object/internals';
 import { RelationshipPayloadsManager } from 'ember-data/-private';
 import DS from 'ember-data';
 import { createStore } from 'dummy/tests/helpers/store';
+import deepCopy from 'dummy/tests/helpers/deep-copy';
 import { module, test } from 'qunit';
 import testInDebug from '../../../helpers/test-in-debug';
 
@@ -45,7 +45,7 @@ test('push one side is polymorphic, baseType then subTypes', function(assert) {
   let id = 1;
 
   function makeHat(type, props) {
-    const resource = copy(props, true);
+    const resource = deepCopy(props);
     resource.id = `${id++}`;
     resource.type = type;
     resource.attributes.type = type;
@@ -89,7 +89,7 @@ test('push one side is polymorphic, subType then baseType', function(assert) {
   let id = 1;
 
   function makeHat(type, props) {
-    const resource = copy(props, true);
+    const resource = deepCopy(props);
     resource.id = `${id++}`;
     resource.type = type;
     resource.attributes.type = type;
@@ -130,7 +130,7 @@ test('push one side is polymorphic, different subtypes', function(assert) {
   let id = 1;
 
   function makeHat(type, props) {
-    const resource = copy(props, true);
+    const resource = deepCopy(props);
     resource.id = `${id++}`;
     resource.type = type;
     resource.attributes.type = type;
@@ -177,7 +177,7 @@ test('push both sides are polymorphic', function(assert) {
   let id = 1;
 
   function makeHat(type, props) {
-    const resource = copy(props, true);
+    const resource = deepCopy(props);
     resource.id = `${id++}`;
     resource.type = type;
     resource.attributes.type = type;