diff --git a/lib/mocha.js b/lib/mocha.js
index 9b3b9e5464..33f359c3b4 100644
--- a/lib/mocha.js
+++ b/lib/mocha.js
@@ -102,7 +102,9 @@ function Mocha(options) {
 
   // files which were in require.cache
   // by the moment of mocha instance creation
-  this._requireCache = this._getRequireCache();
+  this._requireCache = process.browser
+    ? []
+    : this._getRequireCache();
 }
 
 /**
@@ -225,7 +227,10 @@ Mocha.prototype.loadFiles = function(fn) {
     suite.emit('post-require', global, file, self);
   });
 
-  this._flushRequireCache();
+  if (!process.browser) {
+    this._flushRequireCache();
+  }
+
   fn && fn();
 };
 
@@ -258,7 +263,7 @@ Mocha.prototype._growl = function(runner, reporter) {
  * @api private
  */
 Mocha.prototype._getRequireCache = function() {
-  return Object.keys(require.cache || {});
+  return Object.keys(require.cache);
 };
 
 /**