diff --git a/README.md b/README.md
index 053436f59c..06f78f826b 100644
--- a/README.md
+++ b/README.md
@@ -64,7 +64,7 @@ It's as easy as:
  - [Rest parameters](FEATURES.md#rest-parameters)
  - [Spread](FEATURES.md#spread)
  - [Template literals](FEATURES.md#template-literals)
- - [Unicode Regex](FEATURES.md#unicode-regex)
+ - [Unicode regex](FEATURES.md#unicode-regex)
 
 ## Usage
 
@@ -180,7 +180,8 @@ specified in [Polyfill](#polyfill) is also required.
 require("6to5/register");
 ```
 
-**NOTE:** All requires to `node_modules` will be ignored.
+**NOTE:** By default all requires to `node_modules` will be ignored. You can
+override this by passing an ignore regex via `require("6to5/register")(/regex/)`.
 
 ### Browser
 
diff --git a/lib/6to5/index.js b/lib/6to5/index.js
index 568a708aef..e7fcf8e464 100644
--- a/lib/6to5/index.js
+++ b/lib/6to5/index.js
@@ -5,7 +5,7 @@ var _         = require("lodash");
 exports.util = require("./util");
 
 exports.register = function () {
-  require("./register");
+  return require("./register");
 };
 
 exports.polyfill = function () {
diff --git a/lib/6to5/register.js b/lib/6to5/register.js
index 64551e767e..a9a8a9b6c5 100644
--- a/lib/6to5/register.js
+++ b/lib/6to5/register.js
@@ -6,9 +6,11 @@ var old  = require.extensions[".js"];
 
 // TODO: source maps - Error.prepareStackTrace override
 
+var ignoreRegex = /node_modules/;
+
 require.extensions[".js"] =
 require.extensions[".es6"] = function (m, filename) {
-  if (filename.indexOf("node_modules") >= 0) {
+  if (ignoreRegex && ignoreRegex.test(filename)) {
     return old.apply(this, arguments);
   }
 
@@ -20,3 +22,7 @@ require.extensions[".es6"] = function (m, filename) {
 
   m._compile(result.code, filename);
 };
+
+module.exports = function (_ignoreRegex) {
+  ignoreRegex = _ignoreRegex;
+};
diff --git a/register.js b/register.js
index 11d1e33865..a8de654c4b 100644
--- a/register.js
+++ b/register.js
@@ -1 +1 @@
-require("./lib/6to5/register");
+module.exports = require("./lib/6to5/register");