diff --git a/pos_to_weight_by_product_uom/models/__init__.py b/pos_to_weight_by_product_uom/models/__init__.py
index a64cf628af..ca457dc39f 100644
--- a/pos_to_weight_by_product_uom/models/__init__.py
+++ b/pos_to_weight_by_product_uom/models/__init__.py
@@ -1,6 +1,6 @@
-# -*- coding: utf-8 -*-
-# License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl).
+# coding: utf-8
 
+from . import product_product
 from . import product_template
 from . import product_uom
 from . import product_uom_categ
diff --git a/pos_to_weight_by_product_uom/models/product_product.py b/pos_to_weight_by_product_uom/models/product_product.py
new file mode 100644
index 0000000000..f92f3e687c
--- /dev/null
+++ b/pos_to_weight_by_product_uom/models/product_product.py
@@ -0,0 +1,19 @@
+# coding: utf-8
+# Copyright (C) 2018 - Today: GRAP (http://www.grap.coop)
+# @author: Sylvain LE GAL (https://twitter.com/legalsylvain)
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
+
+from openerp import api, models
+
+
+class ProductProduct(models.Model):
+    _inherit = 'product.product'
+
+    @api.multi
+    def onchange_uom(self, uom_id, uom_po_id):
+        res = super(ProductProduct, self).onchange_uom(uom_id, uom_po_id)
+        if uom_id:
+            res = res or {}
+            val = res.setdefault('value', {})
+            val['to_weight'] = self.env['product.uom'].browse(uom_id).to_weigh
+        return res
diff --git a/pos_to_weight_by_product_uom/models/product_template.py b/pos_to_weight_by_product_uom/models/product_template.py
index 25cb4d4ede..cf992eb44b 100644
--- a/pos_to_weight_by_product_uom/models/product_template.py
+++ b/pos_to_weight_by_product_uom/models/product_template.py
@@ -1,7 +1,7 @@
-# -*- coding: utf-8 -*-
-# Copyright 2017, Grap
-# License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl).
-
+# coding: utf-8
+# Copyright (C) 2017 - Today: GRAP (http://www.grap.coop)
+# @author: Quentin DUPONT <quentin.dupont@grap.coop>
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
 from openerp import api, models
 
 
@@ -12,7 +12,9 @@ class ProductTemplate(models.Model):
     def onchange_uom(self, uom_id, uom_po_id):
         res = super(ProductTemplate, self).onchange_uom(uom_id, uom_po_id)
         if uom_id:
-            if res.get('value', False):
-                res['value']['to_weight'] =\
-                    self.env['product.uom'].browse(uom_id).to_weigh
+            res = res and res or {}
+            if not res.get('value', False):
+                res['value'] = {}
+            res['value']['to_weight'] =\
+                self.env['product.uom'].browse(uom_id).to_weigh
         return res