diff --git a/onchange_helper/README.rst b/onchange_helper/README.rst
index 48cca771e..5f75d895d 100644
--- a/onchange_helper/README.rst
+++ b/onchange_helper/README.rst
@@ -24,6 +24,15 @@ Example if you want to create a sale order and you want to get the values relati
 
 Then, `vals` will be updated with partner_invoice_id, partner_shipping_id, pricelist_id, etc...
 
+You can also use it on existing record for example:
+
+    `vals = {'partner_shipping_id: 1'}`
+
+    `vals = sale.play_onchanges(vals, ['partner_shipping_id'])`
+
+Then the onchange will be played with the vals passed and the existing vals of the sale. `vals` will be updated with partner_invoice_id, pricelist_id, etc...
+
+
 Bug Tracker
 ===========
 
diff --git a/onchange_helper/models/ir_rule.py b/onchange_helper/models/ir_rule.py
index b4f67af16..d904a72ab 100644
--- a/onchange_helper/models/ir_rule.py
+++ b/onchange_helper/models/ir_rule.py
@@ -17,7 +17,6 @@ def get_new_values(model, record, on_change_result):
             new_values[fieldname] = value
     return new_values
 
-
 @api.model
 def play_onchanges(self, values, onchange_fields):
     onchange_specs = self._onchange_spec()
@@ -26,7 +25,10 @@ def play_onchanges(self, values, onchange_fields):
     all_values = values.copy()
     for field in self._fields:
         if field not in all_values:
-            all_values[field] = False
+            # If self is a record (play onchange on existing record)
+            # we take the value of the field
+            # If self is an empty record we will have an empty value
+            all_values[field] = self[field]
 
     # we work on a temporary record
     new_record = self.new(all_values)
@@ -39,7 +41,7 @@ def play_onchanges(self, values, onchange_fields):
         all_values.update(new_values)
 
     res = {f: v for f, v in all_values.iteritems()
-           if f in values or f in new_values}
+           if not self._fields[f].compute and (f in values or f in new_values)}
     return res