diff --git a/addons/mrp/models/mrp_workorder.py b/addons/mrp/models/mrp_workorder.py
index 07fd99a99b0..3b380d41921 100644
--- a/addons/mrp/models/mrp_workorder.py
+++ b/addons/mrp/models/mrp_workorder.py
@@ -872,6 +872,10 @@ class MrpWorkorder(models.Model):
             duration += (datetime.now() - time.date_start).total_seconds() / 60
         return duration
 
+    def get_duration(self):
+        self.ensure_one()
+        return sum(self.time_ids.mapped('duration')) + self.get_working_duration()
+
     def action_mark_as_done(self):
         for wo in self:
             if wo.working_state == 'blocked':
@@ -885,7 +889,6 @@ class MrpWorkorder(models.Model):
         for wo in self:
             if wo.working_state == 'blocked':
                 raise UserError(_('Some workorders require another workorder to be completed first'))
-        for wo in self:
             wo.button_start()
 
     def action_mass_pause(self):
diff --git a/addons/mrp/static/src/widgets/timer.js b/addons/mrp/static/src/widgets/timer.js
index b327bc25f97..c65101586bc 100644
--- a/addons/mrp/static/src/widgets/timer.js
+++ b/addons/mrp/static/src/widgets/timer.js
@@ -104,12 +104,11 @@ class MrpTimerField extends Component {
                 !this.props.record.model.useSampleModel &&
                 this.props.record.data.state == "progress"
             ) {
-                const additionalDuration = await this.orm.call(
+                this.duration = await this.orm.call(
                     "mrp.workorder",
-                    "get_working_duration",
+                    "get_duration",
                     [this.props.record.resId]
                 );
-                this.duration += additionalDuration;
             }
         });
         onWillUpdateProps((nextProps) => {