diff --git a/facho/model/fields/one2many.py b/facho/model/fields/one2many.py
index 571f61d..231874b 100644
--- a/facho/model/fields/one2many.py
+++ b/facho/model/fields/one2many.py
@@ -1,11 +1,46 @@
 from .field import Field
 
-class BoundModel:
-    def __init__(self, creator):
+# TODO(bit4bit) lograr que isinstance se aplique
+# al objeto envuelto
+class _RelationProxy():
+    def __init__(self, obj, inst, attribute):
+        self.__dict__['_obj'] = obj
+        self.__dict__['_inst'] = inst
+        self.__dict__['_attribute'] = attribute
+
+    def __getattr__(self, name):
+        if (name in self.__dict__):
+            return self.__dict__[name]
+
+        return getattr(self.__dict__['_obj'], name)
+
+    def __setattr__(self, attr, value):
+        # TODO(bit4bit) hacemos proxy al sistema de notificacion de cambios
+        # algo burdo, se usa __dict__ para saltarnos el __getattr__ y generar un fallo por recursion
+        for fun in self.__dict__['_inst']._on_change_fields[self.__dict__['_attribute']]:
+            fun(self.__dict__['_inst'], self.__dict__['_attribute'], value)
+
+        return setattr(self._obj, attr, value)
+
+class _Relation():
+    def __init__(self, creator, inst, attribute):
         self.creator = creator
+        self.inst = inst
+        self.attribute = attribute
+        self.relations = []
 
     def create(self):
-        return self.creator()
+        n_relations = len(self.relations)
+        attribute = '%s_%d' % (self.attribute, n_relations)
+        relation = self.creator(attribute)
+        proxy = _RelationProxy(relation, self.inst, self.attribute)
+
+        self.relations.append(relation)
+        return proxy
+
+    def __len__(self):
+        return len(self.relations)
+
 
 class One2Many(Field):
     def __init__(self, model, name=None, namespace=None, default=None):
@@ -13,13 +48,16 @@ class One2Many(Field):
         self.field_name = name
         self.namespace = namespace
         self.default = default
-        self.count_relations = 0
+        self.relation = None
         
     def __get__(self, inst, cls):
         assert self.name is not None
-        def creator():
-            attribute = '%s_%d' % (self.name, self.count_relations)
-            self.count_relations += 1
-            return self._create_model(inst, name=self.field_name, model=self.model, attribute=attribute)
 
-        return BoundModel(creator)
+        def creator(attribute):
+            return self._create_model(inst, name=self.field_name, model=self.model, attribute=attribute)
+        
+        if self.relation:
+            return self.relation
+        else:
+            self.relation = _Relation(creator, inst, self.name)
+            return self.relation
diff --git a/tests/test_model.py b/tests/test_model.py
index 34f972b..159b5d2 100644
--- a/tests/test_model.py
+++ b/tests/test_model.py
@@ -416,3 +416,29 @@ def test_model_one2many():
     line = invoice.lines.create()
     line.quantity = 5
     assert '<Invoice><Line quantity="3"/><Line quantity="5"/></Invoice>' == invoice.to_xml()
+
+
+def test_model_one2many_with_on_changes():
+    class Line(facho.model.Model):
+        __name__ = 'Line'
+
+        quantity = fields.Attribute('quantity')
+        
+    class Invoice(facho.model.Model):
+        __name__ = 'Invoice'
+
+        lines = fields.One2Many(Line)
+        count = fields.Attribute('count', default=0)
+        
+        @fields.on_change(['lines'])
+        def refresh_count(self, name, value):
+            self.count = len(self.lines)
+
+    invoice = Invoice()
+    line = invoice.lines.create()
+    line.quantity = 3
+    line = invoice.lines.create()
+    line.quantity = 5
+
+    assert len(invoice.lines) == 2
+    assert '<Invoice count="2"><Line quantity="3"/><Line quantity="5"/></Invoice>' == invoice.to_xml()