diff --git a/erpnext/payroll/doctype/salary_slip/salary_slip.py b/erpnext/payroll/doctype/salary_slip/salary_slip.py
index 60aff02..1f8bfea 100644
--- a/erpnext/payroll/doctype/salary_slip/salary_slip.py
+++ b/erpnext/payroll/doctype/salary_slip/salary_slip.py
@@ -1123,6 +1123,7 @@
 	#calculate total working hours, earnings based on hourly wages and totals
 	def calculate_total_for_salary_slip_based_on_timesheet(self):
 		if self.timesheets:
+			self.total_working_hours = 0
 			for timesheet in self.timesheets:
 				if timesheet.working_hours:
 					self.total_working_hours += timesheet.working_hours