diff --git a/addons/mcs_operating_system/models/project.py b/addons/mcs_operating_system/models/project.py
index c8aeb81..89a4e1e 100644
--- a/addons/mcs_operating_system/models/project.py
+++ b/addons/mcs_operating_system/models/project.py
@@ -186,7 +186,9 @@ class ProjectProject(models.Model):
             for task in project.tasks:
                 if task.write_date:
                     progress_dates.append(fields.Date.to_date(task.write_date))
-            progress_dates.extend(project.timesheet_ids.mapped("date"))
+            progress_dates.extend(
+                date for date in project.timesheet_ids.mapped("date") if date
+            )
             last_progress = max(progress_dates) if progress_dates else False
             project.mcs_last_meaningful_progress_date = last_progress
             project.mcs_days_since_meaningful_progress = (