diff --git a/bin/6to5/dir.js b/bin/6to5/dir.js
index af383a765d..a8e7dc5d79 100644
--- a/bin/6to5/dir.js
+++ b/bin/6to5/dir.js
@@ -17,7 +17,7 @@ module.exports = function (commander, filenames, opts) {
     var dest = path.join(commander.outDir, relative);
 
     var data = util.compile(src, {
-      sourceFileName: path.relative(dest + '/..', src)
+      sourceFileName: path.relative(dest + "/..", src)
     });
 
     if (commander.sourceMaps) {