diff --git a/speedtest.py b/speedtest.py
index 6a2b6b0..0d2ea7d 100755
--- a/speedtest.py
+++ b/speedtest.py
@@ -1079,13 +1079,11 @@ class Speedtest(object):
         for i, size in enumerate(sizes):
             # We set ``0`` for ``start`` and handle setting the actual
             # ``start`` in ``HTTPUploader`` to get better measurements
+            data = HTTPUploaderData(size, 0, self.config['length']['upload'])
+            data._create_data()
             requests.append(
                 (
-                    build_request(
-                        self.best['url'],
-                        HTTPUploaderData(size, 0,
-                                         self.config['length']['upload'])
-                    ),
+                    build_request(self.best['url'], data),
                     size
                 )
             )