diff --git a/addons/project_timesheet/project_timesheet_view.xml b/addons/project_timesheet/project_timesheet_view.xml
index f8c25f4cb33..56dfa068b21 100644
--- a/addons/project_timesheet/project_timesheet_view.xml
+++ b/addons/project_timesheet/project_timesheet_view.xml
@@ -11,7 +11,7 @@
                     <group colspan="4" col="4">
                         <separator colspan="4" string="Invoicing Data"/>
                         <field name="pricelist_id" domain="[('type','=','sale')]" widget="selection"/>
-                        <field name="to_invoice" widget="selection" string="Invoice Task Work"/>
+                        <field name="to_invoice" widget="selection" string="Invoice Task Work" attrs="{'required':[('partner_id','!=',False)]}"/>
                         <field name="amount_max" groups="base.group_extended"/>
                         <field name="amount_invoiced" groups="base.group_extended"/>
                     </group>