diff --git a/facho/model/__init__.py b/facho/model/__init__.py
index fe8cc66..13d7c13 100644
--- a/facho/model/__init__.py
+++ b/facho/model/__init__.py
@@ -31,6 +31,12 @@ class ModelBase(object, metaclass=ModelMeta):
     def __before_xml__(self):
         pass
 
+    def __default_set__(self, value):
+        return str(value)
+    
+    def _set_content(self, value):
+        self._text = str(self.__default_set__(value))
+
     def _hook_before_xml(self):
         self.__before_xml__()
         for field in self._fields.values():
diff --git a/facho/model/fields/many2one.py b/facho/model/fields/many2one.py
index 7f5e35f..4b5caaa 100644
--- a/facho/model/fields/many2one.py
+++ b/facho/model/fields/many2one.py
@@ -29,7 +29,7 @@ class Many2One(Field):
         if callable(setter):
             setter(inst_model, value)
         else:
-            inst_model._text = str(value)
+            inst_model._set_content(value)
 
 
 
diff --git a/facho/model/fields/model.py b/facho/model/fields/model.py
index 073504d..9653f5a 100644
--- a/facho/model/fields/model.py
+++ b/facho/model/fields/model.py
@@ -14,7 +14,7 @@ class Model(Field):
 
     def __set__(self, inst, value):
         obj = self._create_model(inst)
-        obj._text = str(value)
+        obj._set_content(value)
 
     def _create_model(self, inst):
         try:
diff --git a/tests/test_model.py b/tests/test_model.py
index cfcd65c..4b1011b 100644
--- a/tests/test_model.py
+++ b/tests/test_model.py
@@ -272,3 +272,19 @@ def test_field_function_only_setter():
     person.password = 'calculate'
     assert '<Person hash="calculate+2"/>' == person.to_xml()
     
+
+def test_model_set_default_setter():
+    class Hash(facho.model.Model):
+        __name__ = 'Hash'
+
+        def __default_set__(self, value):
+            return "%s+3" % (value)
+
+    class Person(facho.model.Model):
+        __name__ = 'Person'
+
+        hash = fields.Many2One(Hash)
+
+    person = Person()
+    person.hash = 'hola'
+    assert '<Person><Hash>hola+3</Hash></Person>' == person.to_xml()