diff --git a/addons/product/product.py b/addons/product/product.py
index ce5b9bacddf..abdbcaf4895 100644
--- a/addons/product/product.py
+++ b/addons/product/product.py
@@ -152,6 +152,7 @@ class product_uom(osv.osv):
     _defaults = {
         'active': 1,
         'rounding': 0.01,
+        'factor': 1,
         'uom_type': 'reference',
     }
 
diff --git a/addons/product/product_view.xml b/addons/product/product_view.xml
index a59a77c1357..f0908ddc46e 100644
--- a/addons/product/product_view.xml
+++ b/addons/product/product_view.xml
@@ -424,7 +424,7 @@
                                 <field name="factor"
                                     digits="[42,5]"
                                     attrs="{'invisible':[('uom_type','!=','smaller')],
-                                            'readonly':[('uom_type','!=','smaller')]}"/>
+                                            'readonly':[('uom_type','=','bigger')]}"/>
                                 <field name="factor_inv"
                                     digits="[42,5]"
                                     attrs="{'invisible':[('uom_type','!=','bigger')],