diff --git a/addons/hr/models/hr_employee_base.py b/addons/hr/models/hr_employee_base.py
index 6d5d4cee2f2..fa5318b01f8 100644
--- a/addons/hr/models/hr_employee_base.py
+++ b/addons/hr/models/hr_employee_base.py
@@ -172,7 +172,7 @@ class HrEmployeeBase(models.AbstractModel):
     def _get_employee_working_now(self):
         working_now = []
         # We loop over all the employee tz and the resource calendar_id to detect working hours in batch.
-        all_employee_tz = self.mapped('tz')
+        all_employee_tz = set(self.mapped('tz'))
         for tz in all_employee_tz:
             employee_ids = self.filtered(lambda e: e.tz == tz)
             resource_calendar_ids = employee_ids.mapped('resource_calendar_id')