diff --git a/README.md b/README.md
index f47dbe9e..e0d1ff67 100644
--- a/README.md
+++ b/README.md
@@ -101,7 +101,7 @@ eat: memberAction({
   path: 'eat',
   before(attributes) {
     let payload = this.serialize();
-    payload.data.attributes = assign(payload.data.attributes, attributes);
+    payload.data.attributes = Object.assign(payload.data.attributes, attributes);
     return payload;
   }
 })
@@ -141,7 +141,7 @@ export default DS.Model.extend({
 });
 ```
 
-*Warning* this implemention only works for JSON API, but it should be easy to write your own `after` hook to handle your use case. Have a look at the [implementation of `serializeAndPush`](https://github.com/mike-north/ember-api-actions/blob/master/addon/utils/serialize-and-push.ts) for an example.
+_Warning_ this implementation only works for JSON API, but it should be easy to write your own `after` hook to handle your use case. Have a look at the [implementation of `serializeAndPush`](https://github.com/mike-north/ember-api-actions/blob/master/addon/utils/serialize-and-push.ts) for an example.
 
 ## Customization
 
diff --git a/addon/utils/collection-action.ts b/addon/utils/collection-action.ts
index e390157a..0a5e5c3e 100644
--- a/addon/utils/collection-action.ts
+++ b/addon/utils/collection-action.ts
@@ -1,4 +1,3 @@
-import { assign } from '@ember/polyfills';
 import Model from 'ember-data/model';
 import { Value as JSONValue } from 'json-typescript';
 import { _getModelClass, _getModelName, _getStoreFromRecord, buildOperationUrl } from './build-url';
@@ -25,7 +24,7 @@ export default function collectionOp<IN = any, OUT = any>(options: CollectionOpe
     const fullUrl = buildOperationUrl(model, options.path, urlType, false);
     const data = (options.before && options.before.call(model, payload)) || payload;
     return adapter
-      .ajax(fullUrl, requestType, assign(options.ajaxOptions || {}, { data }))
+      .ajax(fullUrl, requestType, Object.assign(options.ajaxOptions || {}, { data }))
       .then((response: JSONValue) => {
         if (options.after && !model.isDestroyed) {
           return options.after.call(model, response);
diff --git a/addon/utils/member-action.ts b/addon/utils/member-action.ts
index 633d362b..3fa8fca6 100644
--- a/addon/utils/member-action.ts
+++ b/addon/utils/member-action.ts
@@ -1,4 +1,3 @@
-import { assign } from '@ember/polyfills';
 import Model from 'ember-data/model';
 import { Value as JSONValue } from 'json-typescript';
 import { _getModelClass, _getModelName, _getStoreFromRecord, buildOperationUrl } from './build-url';
@@ -23,12 +22,14 @@ export default function instanceOp<IN = any, OUT = any>(options: InstanceOperati
     const adapter = store.adapterFor(modelName);
     const fullUrl = buildOperationUrl(this, path, urlType);
     const data = (before && before.call(this, payload)) || payload;
-    return adapter.ajax(fullUrl, requestType, assign(ajaxOptions || {}, { data })).then((response: JSONValue) => {
-      if (after && !this.isDestroyed) {
-        return after.call(this, response);
-      }
+    return adapter
+      .ajax(fullUrl, requestType, Object.assign(ajaxOptions || {}, { data }))
+      .then((response: JSONValue) => {
+        if (after && !this.isDestroyed) {
+          return after.call(this, response);
+        }
 
-      return response;
-    });
+        return response;
+      });
   };
 }
diff --git a/tests/dummy/app/models/fruit.js b/tests/dummy/app/models/fruit.js
index e3267a77..3cac776b 100644
--- a/tests/dummy/app/models/fruit.js
+++ b/tests/dummy/app/models/fruit.js
@@ -1,5 +1,4 @@
 // BEGIN-SNIPPET fruit-model
-import { assign } from '@ember/polyfills';
 import { collectionAction, memberAction, serializeAndPush } from 'ember-api-actions';
 import DS from 'ember-data';
 
@@ -7,7 +6,7 @@ const { attr, Model } = DS;
 
 function mergeAttributes(attributes) {
   const payload = this.serialize();
-  payload.data.attributes = assign(payload.data.attributes || {}, attributes);
+  payload.data.attributes = Object.assign(payload.data.attributes || {}, attributes);
   return payload;
 }
 const Fruit = Model.extend({