diff --git a/tests/test_file.py b/tests/test_file.py
index 6e69f2b..34b2b5c 100644
--- a/tests/test_file.py
+++ b/tests/test_file.py
@@ -60,6 +60,8 @@ def fn(s):
         fn(cStringIO.StringIO(b))
         fn(buffer(b))  # noqa: F821
 
+    if six.PY3:
+        fn(b)
 
 def test_create_with_url():  # type: () -> None
     f = File.create_with_url(