diff --git a/README.md b/README.md
index d5399e9..c2a3ef1 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,8 @@
 # front-matter
+
+1、es7 {...defaultOptions } => Object.assign
+减少项目有polyfill的需求和问题。
+
 [![build][build-img]][build-url]
 [![coverage][coverage-img]][coverage-url]
 [![npm][npm-img]][npm-url]
diff --git a/index.js b/index.js
index d518f1d..f1c7390 100644
--- a/index.js
+++ b/index.js
@@ -19,7 +19,7 @@ module.exports.test = test
 function extractor (string, options) {
   string = string || ''
   var defaultOptions = { allowUnsafe: false }
-  options = options instanceof Object ? { ...defaultOptions, ...options } : defaultOptions
+  options = options instanceof Object ? Object.assign(defaultOptions, options) : defaultOptions
   options.allowUnsafe = Boolean(options.allowUnsafe)
   var lines = string.split(/(\r?\n)/)
   if (lines[0] && /= yaml =|---/.test(lines[0])) {