Index: mailjam/storage.py
===================================================================
--- mailjam/storage.py	(revision 16)
+++ mailjam/storage.py	(revision 18)
@@ -11,5 +11,5 @@
 """
 
-import os, errno, json
+import os, errno, json, inspect
 
 
@@ -63,6 +63,10 @@
             module = __import__(module_name)
             class_ = getattr(module, class_name)
+            # inspect the class __init__ method, getting a list of
+            # accepted/valid arguments.
+            valid_args = inspect.getargspec(class_.__init__)
+            # then, only accepted parameters will be deserialized
             args = dict((key.encode('ascii'), value) \
-                        for key, value in jobj.items())
+                        for key, value in jobj.items() if key in valid_args[0])
             return class_(**args)
         return jobj