diff --git a/addons/purchase/views/purchase_views.xml b/addons/purchase/views/purchase_views.xml
index a6449d0d863..3ef61a5121b 100644
--- a/addons/purchase/views/purchase_views.xml
+++ b/addons/purchase/views/purchase_views.xml
@@ -249,7 +249,7 @@
                                         force_save="1" optional="show"/>
                                     <field name="product_packaging_qty" attrs="{'invisible': ['|', ('product_id', '=', False), ('product_packaging_id', '=', False)]}" groups="product.group_stock_packaging" optional="show"/>
                                     <field name="product_packaging_id" attrs="{'invisible': [('product_id', '=', False)]}" context="{'default_product_id': product_id, 'tree_view_ref':'product.product_packaging_tree_view', 'form_view_ref':'product.product_packaging_form_view'}" groups="product.group_stock_packaging" optional="show"/>
-                                    <field name="price_unit" attrs="{'readonly': [('invoice_lines', '!=', [])]}"/>
+                                    <field name="price_unit" attrs="{'readonly': [('qty_invoiced', '!=', 0)]}"/>
                                     <field name="taxes_id" widget="many2many_tags" domain="[('type_tax_use','=','purchase'), ('company_id', '=', parent.company_id)]" context="{'default_type_tax_use': 'purchase', 'search_view_ref': 'account.account_tax_view_search'}" options="{'no_create': True}" optional="show"/>
                                     <field name="price_subtotal" widget="monetary"/>
                                 </tree>