diff --git a/pynfe/processamento/serializacao.py b/pynfe/processamento/serializacao.py
index e643f1f..b6c9980 100644
--- a/pynfe/processamento/serializacao.py
+++ b/pynfe/processamento/serializacao.py
@@ -9,6 +9,7 @@ import base64
 import hashlib
 from datetime import datetime
 import re
+import six
 
 
 class Serializacao(object):