diff --git a/view/sale_line_tree.xml b/view/sale_line_tree.xml
index 66292c34f6..9bce7c5245 100644
--- a/view/sale_line_tree.xml
+++ b/view/sale_line_tree.xml
@@ -3,6 +3,6 @@
 this repository contains the full copyright notices and license terms. -->
 <data>
     <xpath expr="/tree/field[@name='product']" position="after">
-        <field name="product_customer"/>
+        <field name="product_customer" optional="1"/>
     </xpath>
 </data>
diff --git a/view/sale_line_tree_sequence.xml b/view/sale_line_tree_sequence.xml
index 66292c34f6..9bce7c5245 100644
--- a/view/sale_line_tree_sequence.xml
+++ b/view/sale_line_tree_sequence.xml
@@ -3,6 +3,6 @@
 this repository contains the full copyright notices and license terms. -->
 <data>
     <xpath expr="/tree/field[@name='product']" position="after">
-        <field name="product_customer"/>
+        <field name="product_customer" optional="1"/>
     </xpath>
 </data>