diff --git a/pyjsonrpc/rpcerror.py b/pyjsonrpc/rpcerror.py
index fe224c8..9f2e608 100644
--- a/pyjsonrpc/rpcerror.py
+++ b/pyjsonrpc/rpcerror.py
@@ -31,7 +31,7 @@ def __init__(self, message = None, data = None, code = None):
         self.message = message or self.message
         self.data = data
         self.code = code or self.code
-        assert self.code, "Error without code is not allowed."
+        assert self.code is not None, "Error without code is not allowed."
 
     def __str__(self):
         return "JsonRpcError({code}): {message}".format(
diff --git a/pyjsonrpc/rpcresponse.py b/pyjsonrpc/rpcresponse.py
index fdfc5f5..f0a34e9 100644
--- a/pyjsonrpc/rpcresponse.py
+++ b/pyjsonrpc/rpcresponse.py
@@ -20,7 +20,7 @@ def __init__(self, code, message, data):
             """
             :param code: Error code
             :param message: Error message
-            :param data: Additional error informations
+            :param data: Additional error information
             """
 
             Bunch.__init__(self)
@@ -29,7 +29,7 @@ def __init__(self, code, message, data):
             self.data = data
 
         def __len__(self):
-            return 1 if self.code else 0
+            return 0 if (self.code is None) or (self.message is None) else 1
 
 
     def __init__(