diff --git a/es6.js b/es6.js
index 060d7a9..4fe3959 100644
--- a/es6.js
+++ b/es6.js
@@ -20,7 +20,11 @@ define([
                     //Do not explicitly handle errors, those should be
                     //visible via console output in the browser.
                     if (xhr.readyState === 4) {
-                        callback(xhr.responseText);
+                        if (xhr.status === 200) {
+                            callback(null, xhr.responseText);
+                        } else {
+                            callback(new Error(xhr.statusText));
+                        }
                     }
                 };
                 xhr.send(null);
@@ -31,7 +35,11 @@ define([
             //Using special require.nodeRequire, something added by r.js.
             var fs = require.nodeRequire('fs');
             fetchText = function (path, callback) {
-                callback(fs.readFileSync(path, 'utf8'));
+                try {
+                    callback(null, fs.readFileSync(path, 'utf8'));
+                } catch (error) {
+                    callback(error);
+                }
             };
         }
 
@@ -80,7 +88,11 @@ return {
             options.sourceFileName = sourceFileName;
             options.sourceMap = config.isBuild ? false : 'inline';
 
-            fetchText(url, function (text) {
+            fetchText(url, function (error, text) {
+                if (error) {
+                    return onload.error(error);
+                }
+
                 var code;
                 try {
                     code = babel.transform(text, options).code;