diff --git a/bin/6to5/dir.js b/bin/6to5/dir.js
index feec11d553..680119cb97 100644
--- a/bin/6to5/dir.js
+++ b/bin/6to5/dir.js
@@ -37,8 +37,13 @@ module.exports = function (commander, filenames, opts) {
     if (stat.isDirectory(filename)) {
       var dirname = filename;
 
-      _.each(util.readdirFilter(dirname), function (filename) {
-        write(path.join(dirname, filename), filename);
+      _.each(util.readdir(dirname), function (filename) {
+        var src = path.join(dirname, filename);
+        if (util.canCompile(filename)) {
+          write(src, filename);
+        } else {
+          outputFileSync(path.join(commander.outDir, filename), fs.readFileSync(src));
+        }
       });
     } else {
       write(filename, filename);
diff --git a/bin/6to5/util.js b/bin/6to5/util.js
index 7cfcbb70ce..14c63f009d 100644
--- a/bin/6to5/util.js
+++ b/bin/6to5/util.js
@@ -12,6 +12,10 @@ exports.readdirFilter = function (filename) {
   });
 };
 
+exports.readdir = readdir;
+
+exports.canCompile = util.canCompile;
+
 exports.addSourceMappingUrl = function (code, loc) {
   return code + "\n//# sourceMappingURL=" + path.basename(loc);
 };