diff --git a/lolex.js b/lolex.js
index b49929af..16eb0b03 100644
--- a/lolex.js
+++ b/lolex.js
@@ -1,23 +1,20 @@
 (function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.lolex = f()}})(function(){var define,module,exports;return (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
 (function (global){
-/*global global, window*/
-/**
- * @author Christian Johansen (christian@cjohansen.no) and contributors
- * @license BSD
- *
- * Copyright (c) 2010-2014 Christian Johansen
- */
-
 (function (global) {
     "use strict";
 
+    var userAgent = global.navigator && global.navigator.userAgent;
+    var isRunningInIE = userAgent && userAgent.indexOf("MSIE ") > -1;
+
     // Make properties writable in IE, as per
     // http://www.adequatelygood.com/Replacing-setTimeout-Globally.html
-    global.setTimeout = global.setTimeout;
-    global.clearTimeout = global.clearTimeout;
-    global.setInterval = global.setInterval;
-    global.clearInterval = global.clearInterval;
-    global.Date = global.Date;
+    if (isRunningInIE) {
+        global.setTimeout = global.setTimeout;
+        global.clearTimeout = global.clearTimeout;
+        global.setInterval = global.setInterval;
+        global.clearInterval = global.clearInterval;
+        global.Date = global.Date;
+    }
 
     // setImmediate is not a standard function
     // avoid adding the prop to the window object if not present
@@ -175,7 +172,7 @@
 
         timer.id = uniqueTimerId++;
         timer.createdAt = clock.now;
-        timer.callAt = clock.now + (timer.delay || (clock.duringTick ? 1 : 0));
+        timer.callAt = clock.now + (parseInt(timer.delay) || (clock.duringTick ? 1 : 0));
 
         clock.timers[timer.id] = timer;
 
diff --git a/package.json b/package.json
index 20c7d546..0c0caf7d 100644
--- a/package.json
+++ b/package.json
@@ -23,9 +23,9 @@
     "prepublish": "npm run bundle"
   },
   "devDependencies": {
-    "eslint": "^3.0.1",
     "browserify": "^13.0.1",
-    "mocha": "^2.5.3",
+    "eslint": "^3.0.1",
+    "mocha": "^3.1.2",
     "mochify": "^2.18.0",
     "referee": "^1.2.0",
     "sinon": "^1.17.4"
diff --git a/src/lolex-src.js b/src/lolex-src.js
index 8ee5b341..6fe865cf 100644
--- a/src/lolex-src.js
+++ b/src/lolex-src.js
@@ -1,21 +1,18 @@
-/*global global, window*/
-/**
- * @author Christian Johansen (christian@cjohansen.no) and contributors
- * @license BSD
- *
- * Copyright (c) 2010-2014 Christian Johansen
- */
-
 (function (global) {
     "use strict";
 
+    var userAgent = global.navigator && global.navigator.userAgent;
+    var isRunningInIE = userAgent && userAgent.indexOf("MSIE ") > -1;
+
     // Make properties writable in IE, as per
     // http://www.adequatelygood.com/Replacing-setTimeout-Globally.html
-    global.setTimeout = global.setTimeout;
-    global.clearTimeout = global.clearTimeout;
-    global.setInterval = global.setInterval;
-    global.clearInterval = global.clearInterval;
-    global.Date = global.Date;
+    if (isRunningInIE) {
+        global.setTimeout = global.setTimeout;
+        global.clearTimeout = global.clearTimeout;
+        global.setInterval = global.setInterval;
+        global.clearInterval = global.clearInterval;
+        global.Date = global.Date;
+    }
 
     // setImmediate is not a standard function
     // avoid adding the prop to the window object if not present