diff --git a/lib/extension-core.js b/lib/extension-core.js
index ee0d7bb1..f841ce36 100644
--- a/lib/extension-core.js
+++ b/lib/extension-core.js
@@ -70,6 +70,8 @@ function core(loader) {
   if (typeof window == 'undefined' &&
       typeof WorkerGlobalScope == 'undefined') {
     baseURI = 'file:' + process.cwd() + '/';
+    if (isWindows)
+      baseURI = baseURI.replace(/\\/g, '/');
   }
   // Inside of a Web Worker
   else if(typeof window == 'undefined') {
diff --git a/lib/polyfill-wrapper-start.js b/lib/polyfill-wrapper-start.js
index 790b7634..bf0482dc 100644
--- a/lib/polyfill-wrapper-start.js
+++ b/lib/polyfill-wrapper-start.js
@@ -11,6 +11,8 @@ $__global.upgradeSystemLoader = function() {
     return -1;
   }
 
+  var isWindows = typeof process != 'undefined' && !!process.platform.match(/^win/);
+
   // Absolute URL parsing, from https://gist.github.com/Yaffle/1088850
   function parseURI(url) {
     var m = String(url).replace(/^\s+|\s+$/g, '').match(/^([^:\/?#]+:)?(\/\/(?:[^:@\/?#]*(?::[^:@\/?#]*)?@)?(([^:\/?#]*)(?::(\d*))?))?([^?#]*)(\?[^#]*)?(#[\s\S]*)?/);
@@ -42,6 +44,9 @@ $__global.upgradeSystemLoader = function() {
       return output.join('').replace(/^\//, input.charAt(0) === '/' ? '/' : '');
     }
 
+    if (isWindows)
+      href = href.replace(/\\/g, '/');
+
     href = parseURI(href || '');
     base = parseURI(base || '');