diff --git a/documentation/api_jszip/external.md b/documentation/api_jszip/external.md
index c0ce2381..a480972f 100644
--- a/documentation/api_jszip/external.md
+++ b/documentation/api_jszip/external.md
@@ -4,12 +4,15 @@ layout: default
 section: api
 ---
 
-JSZip uses polyfills of objects that may not exist on every platform.
+JSZip uses objects that may not exist on every platform, in which case it uses
+a shim.
 Accessing or replacing these objects can sometimes be useful. JSZip.external
 contains the following properties :
 
 * `Promise` : the [Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) implementation used.
 
+The global object is prefered when available.
+
 __Example__
 
 ```js
diff --git a/lib/external.js b/lib/external.js
index cbd69ede..37bd7064 100644
--- a/lib/external.js
+++ b/lib/external.js
@@ -1,6 +1,9 @@
 'use strict';
 
-var ES6Promise = require("es6-promise").Promise;
+// load the global object first:
+// - it should be better integrated in the system (unhandledRejection in node)
+// - the environment may have a custom Promise implementation (see zone.js)
+var ES6Promise = global.Promise || require("lie");
 
 /**
  * Let the user use/change some implementations.
diff --git a/package.json b/package.json
index 807a2762..2620913d 100644
--- a/package.json
+++ b/package.json
@@ -53,6 +53,7 @@
   "dependencies": {
     "core-js": "~2.3.0",
     "es6-promise": "~3.0.2",
+    "lie": "~3.1.0",
     "pako": "~1.0.2",
     "readable-stream": "~2.0.6"
   },
diff --git a/test/asserts/external.js b/test/asserts/external.js
index 10217c2c..e1d522ba 100644
--- a/test/asserts/external.js
+++ b/test/asserts/external.js
@@ -1,34 +1,62 @@
 /* jshint qunit: true */
-/* global JSZip,JSZipTestUtils */
+/* global JSZip,JSZipTestUtils,Promise */
 'use strict';
 
 QUnit.module("external");
 
+/**
+ * Creates a wrapper around an existing Promise implementation to count
+ * calls and detect custom implementations.
+ * @param {Promise} OriginalPromise the promise to wrap
+ * @return {Promise} the wrapped promise
+ */
 function createPromiseProxy(OriginalPromise) {
-    function MyShinyPromise () {
-        OriginalPromise.apply(this, arguments);
+    function MyShinyPromise (input) {
+        if (input.then) { // thenable, we wrap it
+            this._promise = input;
+        } else { // executor
+            this._promise = new OriginalPromise(input);
+        }
         MyShinyPromise.calls++;
     }
     MyShinyPromise.calls = 0;
-    MyShinyPromise.prototype = OriginalPromise.prototype;
-    function proxyMethod(method) {
-        if (typeof OriginalPromise[method] === "function") {
-            MyShinyPromise[method] = function () {
-                MyShinyPromise.calls++;
-                return OriginalPromise[method].apply(OriginalPromise, arguments);
-            };
-        }
-    }
-    MyShinyPromise.prototype.isACustomImplementation = true;
-    for(var method in OriginalPromise) {
-        if (!OriginalPromise.hasOwnProperty(method)) {
-            continue;
-        }
-        proxyMethod(method);
-    }
+    MyShinyPromise.prototype = {
+        then: function (onFulfilled, onRejected) {
+            return new MyShinyPromise(this._promise.then(onFulfilled, onRejected));
+        },
+        "catch": function (onRejected) {
+            return new MyShinyPromise(this._promise['catch'](onRejected));
+        },
+        isACustomImplementation: true
+    };
+
+    MyShinyPromise.resolve = function (value) {
+        return new MyShinyPromise(OriginalPromise.resolve(value));
+    };
+    MyShinyPromise.reject = function (value) {
+        return new MyShinyPromise(OriginalPromise.reject(value));
+    };
+    MyShinyPromise.all = function (value) {
+        return new MyShinyPromise(OriginalPromise.all(value));
+    };
     return MyShinyPromise;
 }
 
+test("JSZip.external.Promise", function (assert) {
+    assert.ok(JSZip.external.Promise, "JSZip.external.Promise is defined");
+    assert.ok(JSZip.external.Promise.resolve, "JSZip.external.Promise looks like a Promise");
+    assert.ok(JSZip.external.Promise.reject, "JSZip.external.Promise looks like a Promise");
+});
+
+test("load JSZip doesn't override the global Promise", function (assert) {
+    if (typeof Promise !== "undefined"){
+        assert.equal(Promise, JSZipTestUtils.oldPromise, "the previous Promise didn't change");
+        assert.equal(Promise, JSZip.external.Promise, "JSZip.external.Promise reused the global Promise");
+    } else {
+        assert.ok(JSZip.external.Promise, "JSZip.external.Promise is defined even if the global Promise doesn't exist");
+    }
+});
+
 test("external.Promise can be replaced in .async()", function (assert) {
     var done = assert.async();
     var OriginalPromise = JSZip.external.Promise;
diff --git a/test/helpers/test-utils.js b/test/helpers/test-utils.js
index ba82717e..bbe541bd 100644
--- a/test/helpers/test-utils.js
+++ b/test/helpers/test-utils.js
@@ -203,5 +203,12 @@
         return base64Dict[input];
     };
 
+
+    if (global.JSZip) {
+        throw new Error("JSZip is already defined, we can't capture the global state *before* its load");
+    }
+
+    JSZipTestUtils.oldPromise = global.Promise;
+
     global.JSZipTestUtils = JSZipTestUtils;
 })(typeof window !== "undefined" && window || global);
diff --git a/test/index.html b/test/index.html
index a966a96d..52c81cf8 100644
--- a/test/index.html
+++ b/test/index.html
@@ -13,6 +13,9 @@
 }
 </script>
 
+<script type="text/javascript" src="helpers/test-utils.js"></script>
+<script type="text/javascript" src="helpers/browser-test-utils.js"></script>
+
 <script type="text/javascript" src="../dist/jszip.js"></script>
 
 <script type="text/javascript">
@@ -68,9 +71,6 @@
 }
 </script>
 
-<script type="text/javascript" src="helpers/test-utils.js"></script>
-<script type="text/javascript" src="helpers/browser-test-utils.js"></script>
-
 <script type="text/javascript" src="asserts/constructor.js"></script>
 <script type="text/javascript" src="asserts/version.js"></script>
 <script type="text/javascript" src="asserts/delete.js"></script>