diff --git a/trytond/trytond/protocols/jsonrpc.py b/trytond/trytond/protocols/jsonrpc.py
index 359c1cab9e..71fd207407 100644
--- a/trytond/trytond/protocols/jsonrpc.py
+++ b/trytond/trytond/protocols/jsonrpc.py
@@ -5,6 +5,7 @@ import datetime
 import gzip
 import json
 from decimal import Decimal
+from types import MappingProxyType
 
 from werkzeug.exceptions import (
     BadRequest, Conflict, Forbidden, HTTPException, InternalServerError,
@@ -100,6 +101,7 @@ JSONEncoder.register(datetime.timedelta,
         '__class__': 'timedelta',
         'seconds': o.total_seconds(),
         })
+JSONEncoder.register(MappingProxyType, dict)
 
 
 def _bytes_encoder(o):
diff --git a/trytond/trytond/protocols/xmlrpc.py b/trytond/trytond/protocols/xmlrpc.py
index bceded3c16..e7234bf770 100644
--- a/trytond/trytond/protocols/xmlrpc.py
+++ b/trytond/trytond/protocols/xmlrpc.py
@@ -6,6 +6,7 @@ import logging
 import xmlrpc.client as client
 # convert decimal to float before marshalling:
 from decimal import Decimal
+from types import MappingProxyType
 
 import defusedxml.xmlrpc
 from werkzeug.exceptions import (
@@ -86,6 +87,7 @@ def dump_struct(self, value, write, escape=client.escape):
 
 client.Marshaller.dispatch[dict] = dump_struct
 client.Marshaller.dispatch[ImmutableDict] = dump_struct
+client.Marshaller.dispatch[MappingProxyType] = dump_struct
 
 
 class XMLRPCDecoder(object):