diff --git a/trytond/protocols/xmlrpc.py b/trytond/protocols/xmlrpc.py
index 32b8a64402..4e6ab53ad7 100644
--- a/trytond/protocols/xmlrpc.py
+++ b/trytond/protocols/xmlrpc.py
@@ -16,7 +16,9 @@ import os
 # convert decimal to float before marshalling:
 from decimal import Decimal
 xmlrpclib.Marshaller.dispatch[Decimal] = \
-    lambda self, value, write: self.dump_long(float(value), write)
+        lambda self, value, write: self.dump_long(float(value), write)
+xmlrpclib.Marshaller.dispatch[type(None)] = \
+        lambda self, value, write: self.dump_bool(bool(value), write)
 
 
 class GenericXMLRPCRequestHandler: