diff --git a/openedx/core/djangoapps/content/block_structure/transformer_registry.py b/openedx/core/djangoapps/content/block_structure/transformer_registry.py
index 93464c5ab2..28deb3c6dd 100644
--- a/openedx/core/djangoapps/content/block_structure/transformer_registry.py
+++ b/openedx/core/djangoapps/content/block_structure/transformer_registry.py
@@ -50,7 +50,7 @@ class TransformerRegistry(PluginManager):
         sorted_transformers = sorted(cls.get_registered_transformers(), key=lambda t: t.name())
         for transformer in sorted_transformers:
             hash_obj.update(transformer.name().encode('utf-8'))
-            hash_obj.update(str(transformer.WRITE_VERSION))
+            hash_obj.update(six.b(str(transformer.WRITE_VERSION)))
 
         return b64encode(hash_obj.digest())