diff --git a/lib/index.js b/lib/index.js
index ad899cae..7b483230 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -2,7 +2,17 @@
 
   'use strict';
 
-  var assign = require('object-assign');
+  var assign = Object.assign || function (target) {
+    for (var i = 1; i < arguments.length; i++) {
+      var source = arguments[i];
+      for (var key in source) {
+        if (Object.prototype.hasOwnProperty.call(source, key)) {
+          target[key] = source[key];
+        }
+      }
+    }
+    return target;
+  };
   var vary = require('vary');
 
   var defaults = {
diff --git a/package.json b/package.json
index e90bac83..35342d59 100644
--- a/package.json
+++ b/package.json
@@ -17,7 +17,6 @@
   },
   "main": "./lib/index.js",
   "dependencies": {
-    "object-assign": "^4",
     "vary": "^1"
   },
   "devDependencies": {