diff --git a/fetch.js b/fetch.js
index f39a983a..6d372304 100644
--- a/fetch.js
+++ b/fetch.js
@@ -107,8 +107,11 @@ export function Headers(headers) {
 Headers.prototype.append = function(name, value) {
   name = normalizeName(name)
   value = normalizeValue(value)
-  var oldValue = this.map[name]
-  this.map[name] = oldValue ? oldValue + ', ' + value : value
+  if (this.has(name)) {
+    this.map[name].push(value)
+  } else {
+    this.map[name] = [value]
+  }
 }
 
 Headers.prototype['delete'] = function(name) {
@@ -117,7 +120,7 @@ Headers.prototype['delete'] = function(name) {
 
 Headers.prototype.get = function(name) {
   name = normalizeName(name)
-  return this.has(name) ? this.map[name] : null
+  return this.has(name) ? this.map[name].join(', ') : null
 }
 
 Headers.prototype.has = function(name) {
@@ -125,13 +128,19 @@ Headers.prototype.has = function(name) {
 }
 
 Headers.prototype.set = function(name, value) {
-  this.map[normalizeName(name)] = normalizeValue(value)
+  this.map[normalizeName(name)] = [normalizeValue(value)]
 }
 
 Headers.prototype.forEach = function(callback, thisArg) {
   for (var name in this.map) {
     if (this.map.hasOwnProperty(name)) {
-      callback.call(thisArg, this.map[name], name, this)
+      if (name === 'set-cookie') {
+        for (var index in this.map[name]) {
+          callback.call(thisArg, this.map[name][index], name, this)
+        }
+      } else {
+        callback.call(thisArg, this.map[name].join(', '), name, this)
+      }
     }
   }
 }
@@ -160,6 +169,16 @@ Headers.prototype.entries = function() {
   return iteratorFor(items)
 }
 
+Headers.prototype.getSetCookie = function() {
+  var items = []
+  if (this.has('set-cookie')) {
+    for (var index in this.map['set-cookie']) {
+      items.push(this.map['set-cookie'][index])
+    }
+  }
+  return items
+}
+
 if (support.iterable) {
   Headers.prototype[Symbol.iterator] = Headers.prototype.entries
 }
diff --git a/test/test.js b/test/test.js
index ce0007c0..285dea59 100644
--- a/test/test.js
+++ b/test/test.js
@@ -337,6 +337,28 @@ exercise.forEach(function(exerciseMode) {
         assert.deepEqual({done: false, value: ['content-type', 'text/html']}, iterator.next())
         assert.deepEqual({done: true, value: undefined}, iterator.next())
       })
+      test('getSetCookie', function() {
+        var headers = new Headers();
+
+        headers.append("Set-Cookie", "x=x");
+        headers.append("Set-Cookie", "y=y");
+
+        assert.equal(headers.get("Set-Cookie"), "x=x, y=y");
+
+        var forEach = []
+        headers.forEach(function(value, key) {
+          forEach.push({value: value, key: key})
+        })
+
+        assert.equal(forEach.length, 2)
+        assert.deepEqual({key: 'set-cookie', value: 'x=x'}, forEach[0])
+        assert.deepEqual({key: 'set-cookie', value: 'y=y'}, forEach[1])
+
+        var getSetCookie = headers.getSetCookie();
+        assert.equal(getSetCookie.length, 2);
+        assert.equal(getSetCookie[0], "x=x");
+        assert.equal(getSetCookie[1], "y=y");
+      })
     })
 
     // https://fetch.spec.whatwg.org/#request-class