classes are not hoisted

src/progress-stream.js

@@ -1,7 +1,5 @@
 'use strict';
 
-exports = module.exports = ProgressStream;
-
 const stream = require('stream'),
     TransformStream = stream.Transform;
 
@@ -42,3 +40,5 @@ class ProgressStream extends TransformStream {
         callback(null);
     }
 }
+
+exports = module.exports = ProgressStream;