diff --git a/index.js b/index.js
index cfbfdac..61c17fa 100644
--- a/index.js
+++ b/index.js
@@ -73,7 +73,7 @@ module.exports = function (browserify, options) {
   // bundles
   var sourceByFile = {};
 
-  browserify.transform(function transform (filename) {
+  function transform (filename) {
     // only handle .css files
     if (!cssExt.test(filename)) {
       return through();
@@ -104,6 +104,10 @@ module.exports = function (browserify, options) {
         console.error(err);
       });
     });
+  }
+
+  browserify.transform(transform, {
+    global: true
   });
 
   // wrap the `bundle` function
diff --git a/tests/.gitignore b/tests/.gitignore
new file mode 100644
index 0000000..cf4bab9
--- /dev/null
+++ b/tests/.gitignore
@@ -0,0 +1 @@
+!node_modules
diff --git a/tests/cases/import-node-module/expected.css b/tests/cases/import-node-module/expected.css
new file mode 100644
index 0000000..f0a88f9
--- /dev/null
+++ b/tests/cases/import-node-module/expected.css
@@ -0,0 +1,3 @@
+._styles__foo {
+  color: #F00;
+}
diff --git a/tests/cases/import-node-module/main.js b/tests/cases/import-node-module/main.js
new file mode 100644
index 0000000..59f8d0d
--- /dev/null
+++ b/tests/cases/import-node-module/main.js
@@ -0,0 +1 @@
+var styles = require('cool-styles/styles.css');
diff --git a/tests/cases/import-node-module/node_modules/cool-styles/styles.css b/tests/cases/import-node-module/node_modules/cool-styles/styles.css
new file mode 100644
index 0000000..092b8ad
--- /dev/null
+++ b/tests/cases/import-node-module/node_modules/cool-styles/styles.css
@@ -0,0 +1,3 @@
+.foo {
+  color: #F00;
+}