diff --git a/addons/mrp/models/mrp_workcenter.py b/addons/mrp/models/mrp_workcenter.py
index 5ef8b09ecea..a46dc2b193e 100644
--- a/addons/mrp/models/mrp_workcenter.py
+++ b/addons/mrp/models/mrp_workcenter.py
@@ -202,8 +202,14 @@ class MrpWorkcenterProductivity(models.Model):
     def _compute_duration(self):
         for blocktime in self:
             if blocktime.date_end:
-                diff = fields.Datetime.from_string(blocktime.date_end) - fields.Datetime.from_string(blocktime.date_start)
-                blocktime.duration = round(diff.total_seconds() / 60.0, 2)
+                d1 = fields.Datetime.from_string(blocktime.date_start)
+                d2 = fields.Datetime.from_string(blocktime.date_end)
+                diff = d2 - d1
+                if (blocktime.loss_type not in ('productive', 'performance')) and blocktime.workcenter_id.calendar_id:
+                    r = blocktime.workcenter_id.calendar_id.get_working_hours(d1, d2, resource_id=blocktime.workcenter_id.resource_id.id)
+                    blocktime.duration = round(r * 60, 2)
+                else:
+                    blocktime.duration = round(diff.total_seconds() / 60.0, 2)
             else:
                 blocktime.duration = 0.0