diff --git a/equipment.py b/equipment.py
index 1d685f5..bf88cfb 100644
--- a/equipment.py
+++ b/equipment.py
@@ -22,6 +22,8 @@ class OpticalEquipment(DeactivableMixin, Workflow, ModelSQL, ModelView):
         'readonly': Eval('state') != 'draft',
     }
 
+    _depends = ['state']
+
     _states_serial={
         'readonly': Eval('state') != 'draft',
     }
@@ -81,7 +83,8 @@ class OpticalEquipment(DeactivableMixin, Workflow, ModelSQL, ModelView):
     warranty = fields.Integer("Warranty",
                               states=_states,)
     serial = fields.Char("Serial", size=None,
-                         states=_states_serial,)
+                         states=_states_serial,
+                         depends=_depends)
     health_register = fields.Char("Health Register", size=None,
                                   states=_states,)
 
@@ -99,9 +102,9 @@ class OpticalEquipment(DeactivableMixin, Workflow, ModelSQL, ModelView):
                                              depends=['propietary'])
 
     purchase_origin = fields.Reference("Purchase Origin", selection='get_origin',select=True,
-                                       states=_states)
+                                       states={'readonly': True})
 
-    del _states
+    del _states_serial, _states, _depends
 
     @classmethod
     def _get_origin(cls):