diff --git a/packages/core/array.js b/packages/core/array.js
index d6820b3..94bd360 100644
--- a/packages/core/array.js
+++ b/packages/core/array.js
@@ -3,7 +3,7 @@ export function arrayUnique(array) {
 }
 
 export function flatten(array) {
-  return array.reduce((flattened, elm) => flattened.concat(elm), []);
+  return [].concat.apply([], array)
 }
 
 export function fromObject(object) {