diff --git a/erpnext/assets/doctype/asset_maintenance/asset_maintenance.py b/erpnext/assets/doctype/asset_maintenance/asset_maintenance.py
index 7551eae229e..224f8136f49 100644
--- a/erpnext/assets/doctype/asset_maintenance/asset_maintenance.py
+++ b/erpnext/assets/doctype/asset_maintenance/asset_maintenance.py
@@ -56,8 +56,7 @@ def assign_tasks(asset_maintenance_name, assign_to_member, maintenance_task, nex
 def calculate_next_due_date(periodicity, start_date = None, end_date = None, last_completion_date = None, next_due_date = None):
 	if not start_date and not last_completion_date:
 		start_date = frappe.utils.now()
-
-	if last_completion_date and (last_completion_date > start_date or not start_date):
+	if last_completion_date and ((start_date and last_completion_date > start_date) or not start_date):
 		start_date = last_completion_date
 	if periodicity == 'Daily':
 		next_due_date = add_days(start_date, 1)
@@ -115,4 +114,4 @@ def get_maintenance_log(asset_name):
         select maintenance_status, count(asset_name) as count, asset_name
         from `tabAsset Maintenance Log`
         where asset_name=%s group by maintenance_status""",
-        (asset_name), as_dict=1)
\ No newline at end of file
+        (asset_name), as_dict=1)