diff --git a/addons/sale_timesheet/models/project.py b/addons/sale_timesheet/models/project.py
index 9940fed70bd..cb0d8c6411e 100644
--- a/addons/sale_timesheet/models/project.py
+++ b/addons/sale_timesheet/models/project.py
@@ -367,7 +367,7 @@ class ProjectTask(models.Model):
             if timesheet.so_line == timesheet.task_id.sale_line_id:
                 delta -= timesheet.unit_amount
             if delta:
-                mapped_remaining_hours[timesheet.task_id._origin.id] += timesheet.so_line.product_uom._compute_quantity(delta, uom_hour)
+                mapped_remaining_hours[timesheet.task_id._origin.id] += timesheet.product_uom_id._compute_quantity(delta, uom_hour)
 
         for task in self:
             task.remaining_hours_so = mapped_remaining_hours[task._origin.id]