diff --git a/tests/test_transformer.py b/tests/test_transformer.py
index <HASH>..<HASH> 100644
--- a/tests/test_transformer.py
+++ b/tests/test_transformer.py
@@ -180,4 +180,4 @@ class TransformerTest(TestCase):
         )
         with patcher:
             response = CustomProxyView.as_view(html5=True)(request, '/')
-            self.assertIn('<!DOCTYPE html>', response.content)
+            self.assertIn(b'<!DOCTYPE html>', response.content)
Updated html5 transform test to support python3