diff --git a/ghost/admin/ember-cli-build.js b/ghost/admin/ember-cli-build.js
index fa81b27fa8..334b6b5709 100644
--- a/ghost/admin/ember-cli-build.js
+++ b/ghost/admin/ember-cli-build.js
@@ -102,7 +102,7 @@ module.exports = function (defaults) {
     let app = new EmberApp(defaults, {
         'ember-cli-babel': {
             optional: ['es6.spec.symbols'],
-            includePolyfill: true
+            includePolyfill: false
         },
         'ember-composable-helpers': {
             only: ['toggle']
diff --git a/ghost/admin/lib/koenig-editor/addon/components/koenig-editor.js b/ghost/admin/lib/koenig-editor/addon/components/koenig-editor.js
index 127009e7d9..044829eb76 100644
--- a/ghost/admin/lib/koenig-editor/addon/components/koenig-editor.js
+++ b/ghost/admin/lib/koenig-editor/addon/components/koenig-editor.js
@@ -221,8 +221,8 @@ export default Component.extend({
         // add our default atoms and cards, we want the defaults to be first so
         // that they can be overridden by any passed-in atoms or cards.
         // Use Array.concat to avoid modifying any passed in array references
-        atoms = Array.concat(defaultAtoms, atoms);
-        cards = Array.concat(defaultCards, cards);
+        atoms = defaultAtoms.concat(atoms);
+        cards = defaultCards.concat(cards);
 
         return assign({
             placeholder: this.placeholder,