diff --git a/supwisdom/protocol/nettrans.py b/supwisdom/protocol/nettrans.py
index 4973c8c..3150414 100644
--- a/supwisdom/protocol/nettrans.py
+++ b/supwisdom/protocol/nettrans.py
@@ -17,7 +17,7 @@
     def __init__(self):
         self.clear()
 
-    def _unicode_str(value):
+    def _unicode_str(self, value):
         if isinstance(value, str):
             return value.decode('utf-8')
         elif isinstance(value, unicode):
@@ -96,7 +96,7 @@
     def __init__(self):
         self.clear()
 
-    def _unicode_str(value):
+    def _unicode_str(self, value):
         if isinstance(value, str):
             return value.decode(SERVICE_ENCODING)
         elif isinstance(value, unicode):