diff --git a/lib/utils.js b/lib/utils.js
index aff31595c9..1125380262 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -166,7 +166,7 @@ exports.files = function(dir, ret){
     path = join(dir, path);
     if (fs.statSync(path).isDirectory()) {
       exports.files(path, ret);
-    } else if (path.match(/\.js$/)) {
+    } else if (path.match(/\.(js|coffee)$/)) {
       ret.push(path);
     }
   });